We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale.

Author Topic: Questions CB and TX base station project  (Read 957 times)

Offline Telegrapher

  • Jr. Member
  • **
  • Posts: 42
  • The Netherlands
  • UVB-76 bought me in the SWL'ing habit.
    • View Profile
    • Email
Questions CB and TX base station project
« on: March 20, 2019, 1847 UTC »
Hi,

I am planning on building a base station at home for basic TX experiments. Starting with CB.

I currently have a CB antenna hooked up to a magnet mount attached to a aluminum plate from a disassembled pc case. With an additional wire of copper going from the antenna to one of the water pipes that are used for the heating temperature in the room.

I need to build a tower still. Which I am planning to do when the weather gets more pleasant later this season.

I watched a lot on the web about things to look out for. Like using a SWR meter. And some other technical details.

It all sounds really complicated to me. RX doesnít really have much technical details to work. But for TX I read several topics talking about risk of the radio burning from the inside when the SWR doesnít match or something.

If anyone has a easy list of tips and/or suggestions I would love to hear them. After I heard about the things that could happen when the antenna isnít attached the right way (the radio might blow up inside, etc) I just unplugged the whole rig and itís sitting in the corner collecting dust.. I really want to be able to experience the real TX without worrying about my radio losing a capacitor or smelling smoke after pushing the TX for a while.

Anything is helpful and appreciated!

Kind regards,
Telegrapher.

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 355
    • View Profile
Re: Questions CB and TX base station project
« Reply #1 on: March 21, 2019, 0727 UTC »
You wont need a TOWER for a CB antenna, just a pole, just bolt it to side of the house.

I guess CB is more popular in the US? it's virtually non existent in the UK.

Yes you will need an SWR meter and it's not complicated to use, just checks your antenna and cable/connectors are good and the correct impedance (50R).

You wont get very far with a CB unless the sunspot cycle is peaking and it's VERY low at the moment.

I'd buy a SH Ham rig and use much lower frequencies as you will get out a lot further.

You'll need a bigger antenna tho'!

Str.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline IZS4

  • Full Member
  • ***
  • Posts: 124
  • Florida
    • View Profile
Re: Questions CB and TX base station project
« Reply #2 on: March 21, 2019, 1446 UTC »
I agree. CB radio is not nearly as active as it was years ago and the sun spots are terrible right now. 'A guy I know" did work a lot of DX from 27.385-27.800 mhz back in the 90's. You should save up and buy a used HF transceiver with general coverage receive. Prices have come down quite a bit. Once you have that you will have a great receiver for the time being and be ready to transmit if you choose to become licensed later on. Building wire antennas is very simple. Especially for receive. I was able to buy an HF rig while studying for my General class. It was great motivation to study. Kind of like having a car that you can't drive!

Offline IZS4

  • Full Member
  • ***
  • Posts: 124
  • Florida
    • View Profile
Re: Questions CB and TX base station project
« Reply #3 on: March 21, 2019, 1454 UTC »
One other thing to mention is that with any receiver or transmitter you need to have a good earth ground. As far has using a wire antenna as long as you have proper feedline with no shorts etc you can do use a simple formula for finding the wire length. FREQ divided by 468 for half wave or FREQ divided by 234 for quarter wave. Once this is done you should be within a safe SWR range and then you can fine tune the antenna. A half wave dipole for CB would be approx 17' 2'' long.

Offline R4002

  • DX Legend
  • ******
  • Posts: 2340
    • View Profile
Re: Questions CB and TX base station project
« Reply #4 on: March 22, 2019, 1353 UTC »
Get your CB antenna outside.  A dipole will provide you with better DX performance (generally) and a vertical (homebrew or buy one of the commonly available base station CB antennas on the market, there are lots of options) will give you better local communications capability.  If you go with the dipole, get it high up in the air.  A vertical mounted high will give you better local coverage.  27 MHz actually works quite well for local coverage with a decent antenna setup.

CB is still popular in the USA, although there is considerable variation depending on where you're located.  CB DXing (and freeband DXing) is very popular in the USA and the Americas in general.  In some areas, local AM or SSB "nets" exist.  Where I live there are several "town channels" or "city channels" in use, basically a home channel that various CBers will hang out on.  The local SSB operators hang out on an out-of-band frequency and the AM operators use channel 14, 22 or 33 depending on which group you're talking about.  Once you get out of the city the rural areas will have a "local channel" or "home channel" that is used for standby purposes.  Trucking companies, construction sites and trucking distribution hubs have their own channels.  So yes, it is extensively used in the USA. 

You'll notice a big different in TX and RX performance with the right antenna for CB.
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline Josh

  • DX Legend
  • ******
  • Posts: 2677
    • View Profile
Re: Questions CB and TX base station project
« Reply #5 on: March 22, 2019, 1651 UTC »
Most cb users employ a vertical antenna, so if the dipole isn't vertically polarised you're hindering local comms quite a bit.

The dx will never notice what polarity the signal starts out with, as once the signal hits the idunosphere it changes polarity, so for dx, polarity is out of your control.

The great thing about 11m/10m is it's often possible to get a antenna up a wavelength, where some magic happens compared to when the same antenna sits only a 1/4 off the ground or at ground level.

Also, the vertical will almost always have a lower angle of radiation, happily this is best for local and dx comms both at this frequency range.


nerdstuff;
https://www.w8ji.com/VHF%20mobile%20vertical.htm
http://www.antentop.org/w4rnl.001/gup8.html

In the above infos we see that half wave antennas are best for getting more power out at a lower angle of radiation than 1/4 or 5/8 wl antennas.
Conveniently located near Vincennes Indiana.

Offline R4002

  • DX Legend
  • ******
  • Posts: 2340
    • View Profile
Re: Questions CB and TX base station project
« Reply #6 on: March 22, 2019, 1759 UTC »
Josh makes some good points.  I've had excellent DX results with an 11 meter dipole and various verticals - specifically a homemade 1/4 wave ground plane based off a 108 inch steel whip (102 inch whips are also commonly used) and a ground plane system.  The Antron-99 or A-99 type antennas (verticals) are also quite effective, especially when used with a ground plane kit. 

As mentioned, get the antenna up high and, if possible, use a vertical.  Ideally you would want to have both a dipole and a vertical and the capability to switch between the two but space limitations and other things can make that impractical.  Use high quality coaxial cable to connect your antenna to your radio and make sure to check your SWR with any antenna installation you do. 

What sort of CB capability are you looking to have?  Basic 40 channel AM?  40 channel AM and SSB?  Freeband AM and SSB (access to the 40 legal CB channels plus frequencies above and below the CB band?) or do you want transmit capability for all of HF?  That is, 1.6 to 30 MHz instead of 26.965-27.405 MHz (40 channel CB) or 26-28 MHz/26-30 MHz (freeband 11 meter CB). 

If you're going to go through the trouble of setting up a base station CB antenna I recommend getting a radio that can do SSB in addition to AM.  Access to the frequencies above CB channel 40 and below CB channel 1 - aka the "freeband" or 11 meters, roughly 26 to 28 MHz, with the CB band occupying 26.965 MHz to 27.405 MHz and SSB means you have DX capability when the conditions are right.  Unfortunately right now the solar cycle isn't very supportive of 11 meter DX but you do have sporadic-E propagation and of course local communications. 

CB is how many radio hobbyists first got into the magic of radio.  It's how I started, with a basic 40 channel AM RadioShack mobile CB radio and a magnetic mount antenna.  CB has a magic of its own and is a great springboard into the exciting world of radio.
« Last Edit: March 22, 2019, 1808 UTC by R4002 »
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline ChrisSmolinski

  • Administrator
  • Marconi Class DXer
  • *****
  • Posts: 22331
  • Westminster, MD USA
    • View Profile
    • Black Cat Systems
Re: Questions CB and TX base station project
« Reply #7 on: March 22, 2019, 2007 UTC »
I have a dipole for 11m, not sure how high it is, perhaps 40 or so feet? Seems to work pretty well for DX when the band is open (which if course is not often during this part of the solar cycle). It does pick up locals, but reception could indeed be hindered by the polarization. I'm not enough of an enthusiast (yet?) to put up a vertical.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
NRD 545 / netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 270 ft west-south-west beverage / 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop

Offline R4002

  • DX Legend
  • ******
  • Posts: 2340
    • View Profile
Re: Questions CB and TX base station project
« Reply #8 on: March 23, 2019, 1146 UTC »
Since most local comms are vertically polarized (as previously mentioned) your local performance will be reduced with a dipole.

I've experimented with a sloper-type wire antenna (with a tuner) on 11 meters and have had good experience with local comms - think of that as almost sort of kind of vertically polarized.  I'm sure a proper vertical up 30-40 feet would give you really good results both locally and (when it happens) with long-distance skip propagation.

U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline ThaDood

  • Full Member
  • ***
  • Posts: 249
    • View Profile
    • Extreme Part #15!
    • Email
Re: Questions CB and TX base station project
« Reply #9 on: March 23, 2019, 1902 UTC »
Some of my 1st CB indoor set-ups were portables. 40 channel CB portables that put out a 3-4W carrier on high power, and dropped down to 2W, and some down to lower than 1W, and use the built-in telescopic whip antenna, powered by a 12VDC - 2AMP power supply. About as plug & play as you can get with CB, and some of those older Radio Shack portables from the 1970's, 80's and 90's, were great units that sounded good and were very versatile. Many had External Antenna and MIC connectors. I've surprised some ops when I've told them that I was on a Realistic TRC-221 portable and have had responses like, "That's a portable?!?! I thought that you were base, or mobile!" Just another way to start out in CB. Location is everything as well. Are you a hilltopper, where a portable can get out +20 miles, or are you down in a gully, (Like me.), were you are lucky to hear 5 miles? I've never lived anywhere totally flat, like the Texas Panhandle, but I've been told that +10 miles is nothing in a location like that. A passing thought on another option to consider, and fairly affordable. Most being sold on ebay are from hunters that used these CB portables to hunt with 30-some years ago, but now use FRS, or MURS. 
From DC to light, I take a huge spectrum bite!

Offline Telegrapher

  • Jr. Member
  • **
  • Posts: 42
  • The Netherlands
  • UVB-76 bought me in the SWL'ing habit.
    • View Profile
    • Email
Re: Questions CB and TX base station project
« Reply #10 on: March 24, 2019, 1029 UTC »
Hello all, thanks for the nice responses. They are very useful for my summer project I am building throughout this year. I just hooked a vertical CB antenna to the wall near a fence covering my small garden. In the middle of that garden is a antenna pole of 3 meters height with a dipole on top. Covering 24MHz in the total length from both ends of each pole to the other is 3.1 meters in diameter. The center of the dipole is at 1 and the poles are 1.5 meters long each. It worked nice for my first contact. I heard a response saying yes I can hear you but thereís a lot of noise in the background. Tested with the vertical antenna last night but I did not get a response this time. Maybe the conditions arenít that good indeed right now. I live in the Netherlands near a little town where some farmers live. I hear a few on band 7 and 10 during the evening. AM seems to get better to the other end who heard me testing than the FM mode did. I know that most AM stations are from other countries I hear on my little handheld radio. So that makes me think AM travels much larger distances than the FM signals do.

The only little thing I noticed when first operating the CB radio all inside my apartment was that when TX in AM mode, I heard some speakers turn on or make a popping sound even without being connected to any audio system. Maybe the RF is strong enough to feed the speakers lines and activate them somehow  ???

I am planning to get a HAM license later when things get more quiet in my daily routine. I am at the moment just trying and experimenting with little things to get an idea of how to take care of it. So when I have my final project build I donít face the old problems I may experience during this first experimental stage.

The only bad side here is thereís no radio shack or anything similar to go to pick up stuff I need and get information directly from the store. All has to be done mostly on the internet these days. Which gives me less space to talk about everything I do. But Iím glad I found this forum as itís dedicated to all about radio :)

Offline R4002

  • DX Legend
  • ******
  • Posts: 2340
    • View Profile
Re: Questions CB and TX base station project
« Reply #11 on: March 24, 2019, 1157 UTC »
RFI (Radio Frequency Interference) is quite common with home stereo systems, basically the speakers (and the wires connecting them to your stereo) are picking up your signal and thatís whatís causing the strange sounds.  AM CB radio is notorious for causing these issues. 

There are some easy solutions out there.  Get yourself some RF chokes (theyíre little things that snap onto cables and wires and filter out RFI - commonly sold as ďinline interference filterĒ or ďinline noise filterĒ). 

Noise Filter Cable Ring, VSKEY [10 pcs] Anti-Interference Noise Filters Ferrite Core Choke Clip for Telephones,Tvs,Speakers,Video,Radio,Audio Equipment & Appliances Power Audio (10pcs 3.0mm) https://www.amazon.com/dp/B078XKHLKG/ref=cm_sw_r_cp_api_i_Mc3LCbZD40YCW

^ are what you want.  Install them on your speaker cables and on the power cables for your audio equipment itself.  Iíve had success those - I had major interference with a CB installation I had causing interference to my roommateís hi-fi system - he could hear every word I was saying into the mic coming out of his speakers. 

I got a bunch of those snap-on filters and attached them to the speaker cables (three on each line, one as close to the speaker connection as possible, one in the middle of the cable run and one as close to the hi-fi amp speaker connection as possible), installed another on the line-level audio connection from the turntable to the PHONO input on the amplifier and yet another on the AC power cables for the turntable and the amplifier and it solved the interference problem. 

Also, look into getting a low-pass filter for your CB station (installed between the transmitter and antenna).  CB transmitters, like all transmitters, produce harmonics (so in addition to signal at 27 MHz, it makes a much lower power signal at 54 MHz, then an even lower power signal at 81MHz etc).  Putting a low-pass filter that stops all signals above 30 MHz will stop these harmonics from making it to your antenna and help reduce potential interference issues.  Itís also good operating practice to use a low-pass filter anyway. 

« Last Edit: March 24, 2019, 1210 UTC by R4002 »
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 355
    • View Profile
Re: Questions CB and TX base station project
« Reply #12 on: March 25, 2019, 1320 UTC »
Didn't realize you weren't in the US!

Not much on CB in the EU apart from the usual 'noise' from Italy.

With the sunspot count at an all time low I'd stick to much lower frequencies. Above 25MHz You'll here nothing from anywhere other than very local traffic and there won't be much.

However in 5/6 years time it will be rockin'!

Good Luck.

Str.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline R4002

  • DX Legend
  • ******
  • Posts: 2340
    • View Profile
Re: Questions CB and TX base station project
« Reply #13 on: March 25, 2019, 1536 UTC »
In the US (and the rest of the Americas, for that matter), CB radio is the de facto standard long-haul trucker radio.  Even with modern cellular phones and satcom systems (GPS tracking and satcom telemetry systems are very popular with trucking companies) CB radios can be found in the vast majority of 18-wheelers in the USA.  27.185 MHz AM (CB channel 19) is where most of these radios are tuned.  American truckers make extensive use of "export radios" with additional frequencies above and below the CB band, often with a designated "company channel" that is outside the legal 40 CB channels. 

In addition to those types of trucks, CB is heavily used for work site communications between trucks delivering, sand, gravel, building materials, etc.  In more rural areas it is common to see CB antennas on pickup trucks (often used by hunting clubs).  In the part of the country that I live in (roughly halfway between Miami and the Canadian border on Interstate 95) once you get into the rural areas nearly all pickup trucks have CB antennas on them, usually in addition to a VHF antenna (for either VHF business band, MURS - https://www.hfunderground.com/wiki/index.php/MURS [VHF CB], VHF marine band, 2-meter amateur or some combination of those).  CB base station antennas are also a pretty common sight in rural areas (at least in this part of the USA).  Even in the city, there's a healthy local AM and SSB CB presence.  Most of the SSB CBers are also licensed hams who prefer the more "laid-back" atmosphere of 11 meter AM/SSB vs. 2 meter FM for local comms. 

CB antennas are also commonly found on Jeeps and other SUVs that are used off-road.  Some Jeep/4x4 off road clubs require their members to have 40 channel AM CB radios installed for vehicle-to-vehicle communications. 

So yes, CB is still very much alive and active in the USA.  Even if the OP's local CB scene isn't very busy, he will have a blast once the sunspots come back up.  :D   
« Last Edit: March 25, 2019, 1538 UTC by R4002 »
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline Telegrapher

  • Jr. Member
  • **
  • Posts: 42
  • The Netherlands
  • UVB-76 bought me in the SWL'ing habit.
    • View Profile
    • Email
Re: Questions CB and TX base station project
« Reply #14 on: March 25, 2019, 1730 UTC »
Yeah I noticed a few truckers from like Poland that drive all the way down to deliver goods. I discovered a local community here as I hear every evening especially when sunset a lot of talk on band 7. Right now I heard a few conversations. Little noisy but some are close range and came in clearly.

I still havenít got my hands on a SWR meter so I donít TX that much at the moment. Only a few test calls a week to see if someone responds back.

Itís kinda fun to have my first TX device now and I think I can learn a lot from it and take that experience with me to the radio exam for HAM radio. Funny the people locally heard me when I was using my little dipole in the garden as TX antenna once. Operating at the standard 4Watt output. Iím also thinking about buying a amplifier to boost the power up to 250 watt later.

Nice stories tho. I appreciate all the tips and info I have already got from this forum :)