From One Newbie to Another
A Tiny TX -n- Tool Guide For the Perplexed, the Vexed and the Unlearned!
By lysdexia@evansville.net
INTRODUCTION: So you wanna be an FM Broadcast Buccaneer?
Mmmm... Pablum... Mmmmm.... How's about another deeelicious laxative ad?
Mmmmm... Loud demands for purchase of products I don't need, padded out with
Spudulous Cretin music chosen for digestability, blandness, quick
recognition and "broad appeal." *Gak* "News" that can hardly be
distinguished from commercials. "Public" radio that has all syndicated news
and sattelite-fed music from central sources, just like commercial stations.
*Urp*
It's Radio In The `90's.... God, please bring armegeddon and that right
quickly!
...or maybe you would rather help yourself to a chunk of that bandwidth
and do your part as a rational, passionate, thinking human. You can give
your community a _real_ choice, rather than an ongoing Coke/Pepsi ad war
disguised as an "alternative." Imagine: News that actually happened!
Music from local musicians! Letting people tell their stories as they
wish: not in hacked-up slickly edited sound bites designed to create petty
controversies that obscure the real problems in your commmunity.
Alleluja!
It's not as hard as you might think. All it takes is some skull sweat,
patience, time and about 200-500 bucks spread over a couple of months (this
includes tools and stuff- you can get off much cheaper if you are a
student!...) a careful attitude towards the law and an enormous ego!
This little opus is far from comprehensive- but it may help you ask the
right questions later. God knows I have asked (and still ask!) some really
stupid ones. Don't be afraid to look like a dork on usenet! For every
-=Smug_Bastard=- on alt.radio.pirate who makes a nasty, whithering comment
you will have two or three good, helpful suggestions from people who have
made the mistakes for you! (Don't worry pally, you'll make your own!) I
personally am very impatient and suck at details- yet I still have a decent,
clean signal and pretty good range- you can too!
__________________________________________________________________________
PART THE FIRST: Modulating That Electricity Like a Bargain-Basement Tesla!
Or, The Bare Bones Broadcaster Busts the Bandwidth.
To broadcast you must have the following (in order): A purpose, Airspace,
Know-how and tools, a station and listeners.
1. A PURPOSE
You have to supply this from your own head. What do you want to say and
do? Who are you trying to reach? And most importantly: why should your
audience care? Having a good grip on this will help you make intelligent
decisions on everything from content to hardware later. I chose to do my
station because the music scene in my town is great- yet the local stations
are practically all satellite based. This makes it difficult for local
musicians to get space- micropower to the rescue!
2. FINDING AIRSPACE
This is fun work here- Drive around in the area you want to broadcast to in
a car with a good synthesized tuner and find the clear channels! You should
do this in clear and cloudy weather, day and night- find that clear spot.
Interfering with another station's signal not only unduly annoys the
competition, it sucks for the listeners and gives the whole
micro-broadcasting thang a bad image. To really get to your listeners you
have to be clean and clear. Think about it: do you like to listen to a
cruddy signal? Nyet.
You can do a quick search at http://www.jagunet.com/~kodis/station.html. It
will scope the stations in your area and generate a nifty map for you to
use. The problem with trusting this otherwise excellent service is: the
schmucknitians for your local stations may have overmodulated their signal
to make it sound "Louder" in the quest for higher ratings. This means that
their audio going into the transmitter is too strong, which causes the TX to
"splatter" onto other parts of the band near their designated area. This
shithead behavior makes for an fm dial full of crud and will render your
online research less effective. The only way to be sure is to listen around
for a clear spot!
3. KNOW-HOW AND TOOLS
BOOKS (The place to start getting the know-how)
There are several REALLY helpful books out there that can give you a good
understanding of how radio works- The ARRL handbook should be in any public
library and will give you in-depth information on the nitty-gritty of
modulating static to your own ends. Pay _CAREFUL_ attention to the portions
concerned with filtering of your signal!
"The Practical Antenna Handbook" by Joseph Carr (TAB Books, 2nd Ed. ISBN
0070111057) is absolutely invaluble. It will explain the basic of antenna
design and take you well beyond them in no time. If you buy one book in this
hobby I humbly suggest that this be it. One can have a great transmitter
with a bazillion watts and fantastic sound, but if your radiator is not up
to snuff you might as well be sticking your stereo speakers out the window!
If you are an absolute beginner at electricity in general, may I humbly
suggest "Electricty 1-7" by Harry Mileaf (Editor-In-Chief). This is the bomb
book for learning about electricity from the ground up! (groan)
A series of books that can save you time and money in the long run is a
volume or two of Rudolph Graf's "Encylopedia of Electronic Circuits"
(available from www.northcountryradio.com) The volumes are chock full of
power supplies, amps, compressors, limiters and a zillion other things that
you can build for yourself, without shelling out for the expensive stuff....
Read up a little bit before you start into this hobby- it will save you
time, money and, perhaps, your bacon (where the FCC is concerned). Steve
Quest occasionally posts a good intro to radio theory. (Post it again!
Pbpbpbpbpblease!)
4. TOOLS (Most can be found at the local Radio Shark!)
A good, hot soldering iron (around 15-20 watts).
A supply of thin 2% silver solder (really thin! Your dads plumbing solder
won't work- save it for the antennas!)
A Volt-Ohm meter or Digital Multimeter (DON'T SKIMP HERE! YOUR VOM WILL BE
YOUR BEST FRIEND!) LD Brewer sells a nice one with an SWR bridge built in.
A set of small wirecutters, needlenose pliers, (yes!) baby fingernail
clippers, screwdrivers, hacksaw and wire strippers. The usual toolbox
crud.
A set of small files (handy- not imperative though...)
A plastic index box from Wally-Mart or a sewing store to keep all the
miscellaneous electronic crap you will attatch itself to you like stink on a
monkey.
A scientific calculator. (cheap at wal-mart!)
A set of coax crimpers and the fittings of your choice. (Those big CB "f"
connectors are probably best.)
A dummy load for testing your transmitter without hooking it to an antenna.
A low-power one is butt-easy to build! Basically a 50 ohm resistor soldered
ground to + across a coax fitting. (Invaluble!)
A friend with very little feeling in his or her hands to hold stuff for you
while you solder. Radio Shark sells a neato little soldering stand. (I call
mine R2-D2...)
These are the _very_ basic tools you need to put a transmitter together,
build an antenna and get the sucker up in, and on the air. This ain't rock
collectin'! You don't have to buy all this stuff at once- but I gaurantee
that you will own 90% of it before your TX will put out a good signal! Start
getting tools while you are reading. By this time you will be ready to
begin work on your.....
______________________________________________________________________
5. STATION
You will need to gather the following items for a station:
An audio source- a microphone, a tape player, you get the idea.
A mixer- so's you can talk and jam at the same time
A Transmitter (duh)- There is a long list of those below.
An RF amplifier- ditto.
An antenna
Transmitters: A Preamble
The funnest part of this whole hobby is buying, assembling, debugging then
utterly destroying in a fit of rage, your first transmitter. Most people (I
did anyway) start out by purchasing an FM-10a from Ramsey Electronics. They
can be ordered straight from Ramsey or bought from Radio Shark from their
"Unlimited" catalog. These transmitters are, for the most part, crud. They
sound (in my opinion) like shiznit, have lousy range, put out a really
dirty, harmonic laden signal and drift off of their chosen spot on the band
like a demented butterfly. To be fair to Ramsey though, A trained ape could
build an FM-10. If you can follow the easy, complete directions that come
with the FM-10 you can have noise coming from your stereo (and maybe your
neighbors stereo- if he lives less than a block from you) in an evening. I
alternate between wanting to kiss or kill Ramsey. They get lots of people
into the hobby and on the air for cheap- but dang that thing sounds bad!
With a better quality PLL-type kit you will have probably have very few
problems with harmonics and spurious signals- maybe.... the problem is that
when tinkering to get the best power output from your TX (short for
transmitter) you might be putting out bad signal: and without a lot of
really good equipment (like a spectrum anylizer! Yow! $$$$!) you will never
know for sure and be tempted to skip the $15.00 for an output filter. DON'T
DO IT!!! In building an FM-10 you become INTIMATELY FAMILIAR with harmonics!
When first tuning your FM-10 in you will hear at least one. It is not
uncommon for a newbie to actually tune the TX to the harmonic- and get
terrible sound and range. (Hmmmm, how do I know this? Guess.) Ramsey also
sells PLL kits, but both are hampered by the use of the BA1404 chip which
attempts to do everything- stereo, carrier, oscillator and does none of them
really well. These kits are designed to be toys! Think of them as such!
*Whew* Enough of my Ramsey-bashing...
Recently there has been a bit of a renaissance in transmitter kits. Makers
like Panaxis and Free Radio Berkely that produce solid kits have been around
for years. The relative newcomers like Veronica, North Country Radio and
Wavemach seem to be just as nice if not better. Most of the discussion
around the newsgroup have been about personal preferences and price rather
than the all-out flamage that can occur in other areas of the hobby (like
antenna design and How Much Range Can I Expect....). In other words: the
above kits have been reported to be reliable, pretty easy to build and
clean- maybe better than the local commercial station!
Lots of people ask about micropower radio transmitter manufacturers. Here
is a list of sources and their wares I compiled while searching for my own
best choice. Perhaps one of them will be useful to you. I do not claim this
to be the "KING GAWD LIST OF TERRIBLE COMPREHENSION TO WHICH NO MAN MAY ADD
AND SURVIVE!" It is far from comprehensive: to make it thus, please forward
any other addresses, phone, URL or other info on new manufacturers of FM
transmitter kits to me and I will add it to this posting! I do not have
permission from any of the businesses or groups listed herein. I am posting
this as a service to the micropower community and its boosters. Any
mistakes are my own.
I am not an employee or even a buddy with any of these guys. This is not
spam... sorta like potted meat.
_________________________________________________________________________
LD Brewer
Http://www.ldbrewer.com
(800)886-8023
(813) 980-2287
What can I say? These guys kick ass. They have well-deserved rep for
supplying you with the stuff you need and giving advice that you can use. I
cannot say enough good about them! They carry kits from Ramsey, Veronica,
Free Radio Berkely and audio stuff from Dennon and Gemeni. They Rock! Power
Supplies, Wattmeters, Microphones, 7 and 9 Pole Filter kits COMET CFM-95-SL
antennas, Custom Transmitters and lots more!
Try to find it here first!
__________________________________________________________________________
Free Radio Berkely
1442 A Walnut St.
#406
Berkeley CA. 94709
(415)464-3041
Email:frbspd@crl.com
(many of the Kits FRB sells are available from L.D. Brewer-
http://www.ldbrewer.com- as well. You should probably order from them as
they will most likely have the actual kits in stock and will be available to
help should something go awry.)
Steven Dunnifer is fighting the good fight in court and with these kits
(check his homepage!). There have been a few complaints on alt.radio.pirate
about slow service and weird parts substitutions: You should be aware of
this! However, the folks I have communicated with who own his kits say they
work great, are well designed and rugged! I have one of his 20 watt amp and
5 element filter combos and it works great! Guess it's like owning an older
jeep: they are inexspensive and tough, but you gotta have some know-how to
get it going.
(These prices and descriptions are taken from FRB's catalog that I ordered
in November of `96 and may not reflect actual prices.)
1/2 to 1 Watt PLL Transmitter
Full digital PLL control locks the frequency an prevents any drift
from happening. Will easily drive the 6-8, 1-15 and 40 watt amplifier
kits. Easy to assemble. (Available in almost assembled form, just 10-12
components to solder in, for $155)
6 Watt RF Amplifier
Uses a rugged 6 watt transistor. Designed to boost low wattage
transmitters to a bit higher output and will produce up to 8 watts. A very
small and compact circuit 3x1 1/2 in. for 1/2 watt imput drive. Easy Quick
assembly. Requires 12-14 Volts DC at 3/4 to 1 amp for operation.
15 Watt RF amplifier
Uses a very high gain (14db, power gain of at least 25X) RF
transistor to boost a 1/2 watt input to 15 watts. Measures 2 1/12 by 5 in.
and fits into a 4x6 enclosure (available punched and drilled.) Includes
heat sink. Easy, point to point surface mount assembly. Requires 12-14
volts at 2 amps for operation.
(Tons more- I did not include them for brevitys sake)
FILTERS
It is absolutely imperative to use a filter to prevent interference
from harmonics generated by the transmitter. Both these filters start to
roll the signal off at 108-110 MHz or so. Not using a filter will create
problems and give the FCC ammunition to use against microbroadcasters. A
clean signal is essential to the success of this movement.
(WORD! -D)
Output Filter Kit
A seven element low pass filter, composed of 4 coils and 3
capacitors, to flatten those harmonics. This one works well with the 6 watt
ane 15 watt amplifiers.
Heavy Duty Filter Kit
A nine-element low pass filter, which will handle power levels to
at least 100 watts. Use this filter with the 30 or 40 watt amplifiers.
Enclosure is $15.
Lots more available! Dummy loads, antennae, power supplies, coax, etc.
_________________________________________________________________
CANA-KIT
http://www.canakit.com
Don't know much about these kits. They appear to be BA1404-based stereo VFO
kits that tune from 86-98 mhz and claims a range of 500 meters with a whip
antenna.
At $43.95 it might make a good dormcaster...
__________________________________________________________________
Panaxis Productions
Box 130
Paradise CA. 95967-0130
(916) 534-0417
This guy has been selling kits for years and has a reputation for putting
out high-quality products. I will update this to reflect his current
offerings when I recieve his new catalog. (The following was horked from the
LD Brewer Homepage- don't sue me!)
The Panaxis FMX is a PLL based transmitter kit with some very unique
features. Builder selectable audio allows the use of 'PRO' broadcast audio
equipment, consumer line level input, or speaker level audio input. BUILT IN
AGC nixes the need for a limiter if configured in the low impedance design.
Postive NO-TUNE operation is a plus, and frequency selection is easy via the
rotary freq. select switches.
The fellows at LD Brewer and Progressive Concepts sell his TXs and stereo
generators as well.
------------------------------------------------------------
North Country Radio
P.O Box 53
Wykagyl Station,
New Rochelle, N.Y. 10804-0053
(914) 235-6611 Vox
(914) 576-6051 Fax
(518) 854-9280 Tech support
Email: ncradio200@aol.com or 102033,1572@compuserve.com
http://www.northcountryradio.com
For around $75.00 you can get the MPX96- a phase locked loop transmitter
with onboard stereo and preemphasis. It sounds great and is easily strapped
to 150mw output. (one can apply about 18-20v to the output, upgrade some
caps and an output transistor and get reliable signal in the 230 mw area!)
From the NCR web page:
PLL Synthesized for accuracy (0.1 KHz or better, adjustable) with digital
receivers Easy construction and setup, with VOM and audio source RF output
filter for clean RF and low harmonic output less than -50 dBc No obsolete,
drift prone, unstable BA1404 used Excellent audio quality and separation,
noise and spurs -60 dBc or better, separation 30 dB Audio response 20 to
15000 Hz, std preemphasis built in, takes standard line level audio Operates
from 12-14V DC supply at 125 ma Small size 4" X 4", rugged epoxy fiberglass
G-10 PC board used Fits into our NC1500X metal case All signals accessible
for educational and service purposes Covers 88 to 108 MHz and 76-88 MHz
(used in some nations), 100 KHz steps 19 and 38 KHz MPX signals crystal
controlled On board audio generator (1187 Hz) crystal controlled, for
testing.
The MPX96 will be useful anywhere a short range low power FM audio link is
needed. It is far superior to free running FM transmitters and will not
drift off channel, and perfectly compatible with digitally tuned FM
receivers. It is also useful as a teaching aid, unlike low end units using a
BA1404 or other black box IC, allows access to all MPX signal waveforms and
the observation of the process of signal generation. The circuit is
adjustable for optimum performance, and if no test equipment is available,
works well with default settings, so anyone can get satisfactory results
with only a VOM or a DVM. In the USA and certain other countries, signal
radiation must be kept to a level low enough so as not to exceed specific
field strength levels and not to i nterfere with other stations using the FM
broadcast band. Check with the applicable laws in your nation, such as the
FCC or DOT rules and regulations. In the USA Part 15 of the FCC rules and
regulations applies.
(I use this particular TX- I think it godlike!)
______________________________________________________________________________________________________
Veronica Kits
18 Victoria St.
Queensbury, Bradford
BD131AR, UK
44 1247 816 200
http:www.legend.co.uk/~veronica
Veronica has a butt-load of neat, inexpensive kits. The one listed here is
their latest (as of 2-13-97). There are higher powered kits available. They
are distributed in the states by L.D Brewer (L.D. Homebrewer?).
You can reach L.D. Brewer at http://www.ldbrewer.com- and I suggest you do!
The fellows are helpful to the extreme, know what they are talking about and
will not sell you a bunch of crap you don't need. They also have a sense of
humour- which will help you keep your own when you screw up!
TECHNICAL SPECIFICATIONS
Frequency Range: Programmable from 87.5 - 108MHz
Frequency Generation: Crystal referenced Phase Lock Loop
Frequency Stability: Better than +/- 1 KHz max, typ +/- 500Hz
Spurious Emissions: Better than -45dB reference to carrier
RF Power Output: 900mw minimum
RF Output Connector: SO239
Power Supply: 13.8v DC regulated
Audio Input Sensitivity: 0.775 V rms for +/- 75 KHz dev
Signal to Noise Ratio: -75 dBu
Audio Frequency Response: Flat from 20 Hz to 76 KHz
Pre-emphasis None, 50 uS or 75 uS
Audio Distortion: Better than 0.2% THD
Audio Input Connector: Phono Socket
PRICE
KIT FORM: 65 Pounds (english)
ASSEMBLED & TESTED: 99.95 Pounds (english)
___________________________________________________________
WAVEMACH COMMUNICATIONS
320 Dixon Road, Suite 302,
Etobicoke, Ontario
Canada M9R 1S8
(No Email or WWW yet.... pending)
(416) 243-2260 Vox
(416) 243-1067 Fax
(Attendez Vous! Wavemach kits and completed TX's are now available from
Progressive Concepts! See Above!)
This fellow builds the very interesting-looking FMS2 and attendant power
amplifiers, power supplies etc. They are available fully assembled or as
kits (call Progressive Concepts!)
FMS2:
Dual crystal controlled
Dip switch selectable in 100KHz increments
Freq range 75MHz to 125MHz
Automatic level control
2:1 audio compressor
Audio buffer/preamp
High performance preemphasis and roll off filter
RF Metering circuit
Harmonic filter
On board switching power supply
Audio Response: 20-20KHz
Max Audio Level: 245v RMS
Input Impedance: 100K
Output Impedance: 50-75 Ohms
Distortion: 0.2%
Stereo Separation: 40db
Noise: -65db
Deviation: 75 KHz
Output: Ver1 500mw
Ver2 200mw
Spurious Output: -40db
Channel Res.: 100KHz
Freq Range: 75MHz-125Mhz
Current: 500ma
Voltage: 8-12v (12v recommended)
Board Size: 5x6 1/4"
Version 1 (500mw): $295.00 US
Version 2:(200mw): $285.00 US
FMS2 Schematic Only (ver 1&2): $27.00 US
FMB2 Power Booster (2 1/2 watts) $55.00 US
FMB2 Power Booster Schematic Only $12.00 US
5/8 wave Antenna (3.4 dBI) $135.00
Power Supply: $87 (ouch!)
____________________________________________________________________________________________________
6. COAX AND ANTENNAE
Coax
For most low-power applications (a watt or so) Belden RG-58 coax is okay.
For long cable runs or power in the 50 watt or above range one should go for
_at the very least_ RG-8. Get the good stuff with a foam core- the coax I
have gotten from Radio Shark is shite. Make sure you grab a heap of those
nifty little zip-ties too. Electrical tape sucks in high winds, Jimson!
There are some who swear by twinlead (which is supposed to be very low-loss)
but I have never fooled with it.
Below is a synopsis of a conversation that appeared on alt.radio.pirate
concerning coax. I have removed all names exept L.D Brewer's and my own due
to privacy considerations. If you see your words here, and would like to
have your name on them, feel free to email me and I'll put it back!
COAX SHOOTOUT!
Douglas \"Lonely Planet Boy\" Shawhan"
<lysdexia@evansville.NOSPAM.net> wrote:
>Cost-B-damned, No-holds-barred best 50 ohm coax for a run of 100 feet
>pumping 20 watts or more: Your votes?
>d
---------------------------------------------------------
My vote goes for 1-5/8" heliax and larger. Low loss.
---------------------------------------------------------
Well for only 20 watts you can use pretty much anything I would guess
that either RG/59 or RG/58 (one of these is 50ohm, the other is 75ohm).
Both of these are fairly low loss and for 20W you'll have no problems
at all.
If you're going to start pumping more power then I would suggest RG/8 which
offers good power handling and price.
Seriously though - you're only going to encounter problems when you start
upping the power out. I've quite successfully run 75W on the thinner coax
with no problems.
If you aren't getting out well enough some meatier silicon is often cheaper
than a long run of expensive coax.
---------------------------------------------------------
>Well for only 20 watts you can use pretty much anything I would guess
>that either RG/59 or RG/58 (one of these is 50ohm, the other is 75ohm).
>Both of these are fairly low loss and for 20W you'll have no problems
>at all.
>If you're going to start pumping more power then I would suggest RG/8 which
>offers good power handling and price.
>Seriously though - you're only going to encounter problems when you start
>upping the power out. I've quite successfully run 75W on the thinner coax
>with no problems.
>If you aren't getting out well enough some meatier silicon is often cheaper
>than a long run of expensive coax.
Cheaper and dumber. Never mind the loss factors or that the stuff
doesn't last, but cheap, poorly shielded coax also has a rather nasty
tendency to radiate a lot of harmonics and other unwanted garbage.
My personal opinion is that anyone who wants to run 20 watts (or more)
at 100MHz through a hundred feet of RG-59u is either out of their mind
or has no concept of what they are doing. But that's just my personal
opinion:-), *Good* RG-8 is fine for HF but starts to get pretty lossy
at FM broadcast frequencies.
My vote for best stuff cost-be-damned? I'd say get some RG-214u w/the
silver-plated conductors. Goes for a bit more than a buck a foot last
time I checked. A radio tech friend of mine was lucky enough to have
free access to a big spool of this stuff from the shop he worked at --
so he ran it w/ a CB rig! Talk about waste & overkill........
-------------------------------------------------------------------
: Well for only 20 watts you can use pretty much anything I would guess
: that either RG/59 or RG/58 (one of these is 50ohm, the other is 75ohm).
: Both of these are fairly low loss and for 20W you'll have no problems
: at all.
That would be totally INSANE to run any 100 MHz signal for 100 feet on
RG-58 or 59. At least half the power would be lost in the coax. NOT
GOOD!! Use RG-8 at the minimum!
-----------------------------------------------------------
There are many types of coax, some that are made of a solid outside jacket
that looks like the flexible electrical conduit. This is commonly known
as Heliax, but that's a brand name, from Andrew. There are probably
others. It's expensive, too. But it's low loss, since the center
conductor is supported by rings of teflon or something similar. It can
handle a lot of power, thousands of watts. But you said you didn't care
about cost, so..
You could probably get by just fine with the popular and much talked about
Belden 9913.
------------------------------------------------------------
> > Cheaper and dumber. Never mind the loss factors or that the stuff
> > doesn't last, but cheap, poorly shielded coax also has a rather nasty
> > tendency to radiate a lot of harmonics and other unwanted garbage.
>
The quality of coax has nothing to do with the radiation of harmonics.
If your transmitter is generating harmonics, the best coax in the world
will not keep them from being radiated. You must eliminate the harmonics
at the transmitter.
-------------------------------------------------------------------------
Try Belden 9913, short of hard line it is pretty good. You could use the
mini-hardline that is flexible from Andrews as well.
Really Famousguy
--------------------------------------------------------------------------
Hi Doug,
Incredibly Niceguy in England calling.
I'd agree with both ***** and Mr RG-214 above.
There's no such thing as overkill where coax is concerned, especially at
VHF freq's. I'm surprised no ones put Cable X-Perts name forward, they
are down the road from you in IL.
Tech info 847-520-3003, e-mailcxp@ix.netcom.com
Freephone on 800-828-3340 (orders only)
This co' advertises in the ham mags.
Loss factor is loss factor, every db is worth having, get that antenna
up higher than high at VHF, or consider a co-linear, alternatively if
you're on the edge of your town or city consider a directional array.
Several of the FM boys here in London use yagi's from the tops of tall
high rise buildings!
I use Andrews LDF to feed a 340ft wire on 1.8Mhz, also to feed the tower
on this band.
No, there's no such thing as overkill, but will the bank account stand
it?
----------------------------------------------------------------------------
1-5/8 IS nice !! You have to have a good tower just to support the
stuff however ! Currently, I am using 7/8 Andrews, and at 100 Mhz
there is little or no loss.
For the average hobbyist, we recommend Belden ( or equiv. ) 9913.
This is a semi rigid air-dialectric 50 ohm cable, which has about the
same loss at 100 mhz / 100 ft as Andrew 1/2 inch hardline.
We sell the 9913 with connectors attached ( PL-259 ) for $75.00 / 100
We also sell a good quality ( low loss ) RG-8 w/ connectors for
$28.95 / 50 ft , and $42.95 /. 100 ft.
Whatever you do, don't try to run Rat shax RG-8 ( or 58 ) in longer
runs than about 20 feet. The braid is so loose on that stuff that most
of your signal will leave the coax before it ever reaches your antenna !
Remember, a good quality antenna, ( and feedline ) are the MOST
important components of a Micro-Radio station !!!
L.D.Brewer 2-Way Radio
http://www.ldbrewer.com
ldbrewer@flanet.com
1-800-886-8023
----------------------------------------------------------------
Belden 9913
-----------------------------------------------------------------
Has anyone seen the loss specs for the mini-8 coax sold for CB sets or
whatever? I have seen pieces of it, and it's the same size as RG-59, but
has a larger center conductor so it's lower impedance. It has foam
dielectric for low loss. And it's supposed to be better than RG-58. I've
seen it used between a 400 W linear and an antenna, so I know that it
works, at least for CB.
------------------------------------------------------------------------------
>I'm using Belden 8214. Anybody know the difference between 9913 and 8214?
8214 has a foam dialectric.. 9913 is air dialectric, and has a continuous
foil sheild supported by a 90% braid. Very much better than 8214 as a rule.
8214 on the other hand is much better than *most* el-cheapo cable out there !
-------------------------------------------------------------
>
> >You could probably get by just fine with the popular and much talked about
> >Belden 9913.
>
> I'm using Belden 8214. Anybody know the difference between 9913 and 8214?
>
> Thanks
A lot less loss. 9913 is the next best thing to regular old hardline
but costs a lot less, weighs a lot less and is somewhat more flexible.
9913 has a dialectric that is mostly air with a plastic spiral to
keep the co-axis apart. When dealing with low power signals either
transmitting or receiving and runs over about 40 feet it is the
way to go to not loose precious signal... (and not much $$ extra)
--------------------------------------------------------
******, turn down the voltage a minute and spend a few less $$$$$!
This 2013 has almost an air dialectric with the same plastic spiral but
it doesnt sell for a buck or more a foot only 35 cents a foot to
500 then 33 cents a foot.
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Hmmmm... never heard of 2013. The last 50 foot chunk of Belden 9913 I
bought cost me 35 bucks. I have seen it a little less somewhere else
since then, but that is ballpark.
---------------------------------------------------
Go for RGB-213 cable....hardly any loss
----------------------------------------------------
After some more up-to-date reasearch. I must reconsider my vote.
Athough RG-214u still beats the hell out of RG59, I must admit that
it does in fact display a 0.6 dB greater loss factor than Belden 9913
per 100 feet at 100Mhz -- a diffrence which is somewhat academic
considering it would take 500 feet before producing a 3dB diffrence,
which as I'm sure you all know is generally considered the lower limit
of human perception relative to subjective loudness. Nevertheless,
214 does display an obvious and measureable inferiority.
HOWEVER, this does not mean that my vote for "cost be damned
best 50 ohm coax" now goes to 9913. Nay, in fact based on my recent
reasearch I now chose Andrew LDF5-50A. $5.75 per foot.
---------------------------------------------------------
A 1 or 2 Db difference at the transmitter site cannot be noticed at the
receiver. So why the big fuss over fractions of Db loss in coax?
The lowest loss feed line is balanced or open wire (ladder) line. The old
timers knew this and built their antenna systems based upon that fact. VSWR
and line loss is a factor for both transmitting and receiving. An antenna
tuner is used with open wire feed line and a dipole fed this way can
achieve very good results on all the H.F. bands. Hope this helps some....
-----------------------------------------------------------
Heliax 1-5/8'' is best if you
need pretty close to zero loss. Its still expenesive even here
in the us. As another alternative which performs quiet well try
and get some RG-8U 50 ohm heavy duty coax. what ever you deside
on use N connectors at least at the mast end to couple your feedline
to the antenna. And for a good Antenna that offers low angle radiation
use a slim jim, This type of antenna beats hands down even some of
the more aclaimed broadcast type antennas. Works real well if you
stack two of them in a phased array config.
--------------------------------------------------------
Hello:
Normally, the VSWR will not show much of a difference between good and
junk coax at 100 feet. What will happen is a MAJOR power loss at
higher frequencies.
Try this. Get 100 feet or so of good ole junk RG-58. Hook up the
transmitter to one end and a dummy load or antenna to the other. First
hook up a power meter between the transmitter and the coax. Take a
measurement. Then put the power meter on the other end between the
coax and antenna. At 400mhz or so, you will see about a 15x drop in
power!!!! Put 30 watts in and you get about 2 out!!! At HF, the losses
are much much less. I don't have a chart in front of me, but I seem to
remember about a 1 to 2 db loss at 20 meters. Most coax shows a
fairly linear loss as frequencies increase.
Remember that a 3 db loss is HALF POWER LOSS! Every db is huge when
driving the antenna. At microwave frequencies, the hardline coax can
cost way more than the radio itself.
Hope this helps.
-------------------------------------------------------------
I am just a dumb ham but it is a shitload cheaper and a hell of a lot
better to mount the amplifier on the antenna mast or tower and run the
DC power and RF through some relatively cheap coax. You will also get
all of the amps power to the antenna this way. It's your money though.
------------------------------------------------------------------
------------------------------------------------------------------
So there you have it: the overwhelming majority go for Belden 9913 as the
best compromise. Dissenting votes go for hardline or putting your amp up on
the antenna mast. (dc power loss over long distance make this a dubious
proposition unless you have a power supply that can handle the vagaries of
weather..)
Antennas
Hold on! This is where the big flames start! There are several different
types of antennas, and the one you use can depend on your skill level,
your cash flow and your directional needs. There are many more types of
antennas than I list here- check the ARRL Antenna book for more.
An antenna is a radiator that sends your signal to the reciever. A properly
tuned antenna is your key to longer range and a good, strong signal. In
fact, a good antenna is more likely to give you range than masses of power!
There are a couple of things to consider when choosing your antenna. First
is polarization. Most commercial stations are circularly polarized. The
simple explaination is that the signal coming from a circularly polarized
antenna is picked up equally well by an auto antenna (vertically polarized,
meaning it is vertical to the earth, or ground plane) or a home stereo
(horizontally polarized). The main drawback to circular polarization is that
you get negative gain. (More on gain is later. For now think: "More gain
good, less gain bad.") That is why you see some commercial stations with
several "bays" of weird-looking curliques going up and down the tower:
having three or more "bays" helps to make up for the loss inherent in the
design and get more gain by adding more length to the radiator. If your
audience is going to be folks in cars and students in dorms listening in on
cheap jamboxes, then you probably want to go with vertical polarization. If
your listeners will be owners of nice home stereos- horizontal. And there is
always the dreaded cross-polarized dipole!
Seriously folks, most of us are operating at around 1-20 watts, so a
vertically polarized gain antenna like a J-Pole, Ground Plane or a Yagi is
probably best.
I will tell how I made a dipole and a J-Pole, and give overviews and
follow-up info on others and update this as I experiment with them.
DIPOLE
This is the easiest antenna to make. The recipe I used for a dipole is
basically two 1/4 wavelength pieces of 1/2" copper tube set end-to-end with
a 50 ohm balun between. The + lead from the balun goes to one side, the -
lead to the other. Here is how I built mine:
First, the math. Divide 234 by your wavelength (say 89.5). This will give
you the length of your elements in feet.
To wit: 234 \ 89.5 = 2.61 feet.
Now I don't know about you, but I don't relish trying to figure out .61
feet- it seems dumb. So I always convert to metric like so:
2.61 feet x 12 = 31.32 inches, 31.32 inches x 2.54 = 79.5 cm
So there you have it: two elements 79.5 cm long!
It is a _lot_ easier to get an accurate measurement this way than futzing
around with all the fractions, don't you think? (If any of you Euro Cats
can clue us into the straight-from-metric measurement I will be happy to
put it in here- we are silly here in the states!)
I made a simple set of sliding elements for my dipole for fine-tuning
thusly: cut your dipole elements about 1/2" short. Take two 3" sections of
scrap copper tubing and cut a 1/4" longitudinal section from them (that's
"longways") Squash the sliders a little and slide them into the outer ends
of your elements. They should be pretty tight. Sliding elements for $0! (If
you really want to be clever, I guess you could put copper caps on the end,
but mine worked fine without them.) I mounted mine on a 3 foot board by
drilling through an inch from the edge every 8 inches and putting a zip-tie
through the hole and around the elements. I just nailed it vertically to my
windowsill! (watch for metal gutters a wavelength or less away!) Tune with
an SWR meter and you are ready to go!
A properly tuned dipole has no gain, but that is no biggy as it is not
particularly lossy either. Make sure you use a 50 ohm balun! Not using a
balun causes your feedline (the cable from the transmitter to the antenna)
to radiate signal. That makes for a weaker signal at the antenna high SWR
(Standing Wave Ratio) and terrible range. Don't be fooled like I was and use
one of those stupid tv 300 to 75 ohm baluns from the Radio Shark! Get a good
50 ohm from a ham supplier!
CROSS-POLARIZED DIPOLE
Very similar to a regular dipole. Just add two more elements in an "X"
pattern so that you have two negative and two positive elements at right
angles to each other. Put on crossed boards and mount like you would a
regular dipole. Weave yarn through it to get that macrame' look (this is
called the "Jan Brady" camoflage effect) and your landlord will think it is
a `70's wall hanging or a dream catcher. Kill me.
The main drawback in a cross-polarized dipole is that it has negative gain,
like a circularly polarized antenna. This is no big deal if you have a small
area to cover (like a small college campus) or have power to burn. You will
probably need at least five watts to get a 3/4 mile radius with a cross-dipole
on the third floor of a building......
J-POLE
Talllllllll antenna! Good gain, fairly easy to tune and make with two pieces
of 1/2" copper water pipe, a hacksaw, torch, some solder and flux paste and
a fist full o' zipties! This is the second antenna I built and I had fairly
good luck with it.
A J-Pole is (duh) shaped like a letter `J'. The tall part of the `J'
recieves the + side of your coax. The small part gets the - side.
Please see
http://www.svn.net/mycal/mpr/jpole.htm
for the plans I used.
GROUND PLANE
More to come!
YAGI
More to come
PART THE SECOND: LEGALITY. AIEEEEEE!
___________________________________________________________
This file was written using the Joe text editor under Linux
1.2.13- Free Unix! Free Radio! Free Humans! All props to
those who helped me and others get our mouths on the ether!
___________________________________________________________
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