CB repeater

[towerdog]

Today it just occured to me, that older CB's could in theory be easily modified for repeater offset. I would have to get the calculator out and open up an old 23 channel unit to prove this theory, but it could be as simple as rearranging the crystal banks and vola, you have offset for repeater.

So take a pair of old radios, make cable from speaker output to mic input, and mic input to speaker output, some kind of transistor switching to PTT wire, wrap it all up with black tape in a 5 gallon bucket and throw in some AGM batteries, a coax and wire dipole. take it out in the woods and set it on top of the highest hill, and the woods are covered till the batteries die.

I know, I doubt anybody cares, CB is all about high power amps and brute power.

Does this theory sound plausable, it is kinda pointless but it might give someone new use out of some old 23 chanel units.

 

[Sonwatcher]

A few years ago there were a couple freeband repeaters. There was a thread or 2 on this forum about them. Not sure how they did it.

 

[15minigrass]

Cbers love the challenge of making DX the way it was meant to, skips. I think it would work thou. LMK if it works out. Jim...

 

[Robalo]

north ca cbs use this program

eQSO Software Download Page

 

[towerdog]

north ca cbs use this program

eQSO Software Download Page

Did I get this correct, packet over CB, now that is strange (from someone who's talking about CB repeaters).

 

[W5LZ]

Is a CB repeater possible? Yes. The frequency of use isn't the biggy.

Is a CB repeater practical? Not really. How do the users do that TX/RX off setting? And the really 'biggy', how do you get people to not interfere with it? I don't think there's a can big enough to hold all them worms!

Packet, or any other mode on CB? If it's AM or SSB based, it's certainly possible. Almost any mode can be 'produced' using a computer. The biggy is still going to be getting people to leave you alone while doing it (which says nothing about the legality of it). How about PSK31? Talk about a low power mode, that has got to be it. Same thing though, "Leave us alone!" just won't cut it I'm afraid.
- 'Doc

 

[Captain Kilowatt]

The big thing about a CB repeater is the duplexer required to isolate the RX from the TX. They are quite large for 11m and just plain not available so you would have to build your own from scratch which is a bit tricky unless you know exactly what you are doing and have the test gear to properly construct and test one.Even retuning one from the high end of 10m is pretty much a no-go because you would have to add length to the section which is a lot harder than taking it away.

 

[towerdog]

knew I forgot some detail. cant tx and rx at the same time without the di-plexer. All the lo-band systems I have seen had offests in the range of megahertz, at least 3 or 4 Mhz, so what is available for lo-band will not work, at least very well.

Isolation will be a problem indeed. I have seen setups where the seperate TX and RX antennas were vertically seperated by about 100 feet or so. I have a nice system for 'casting' dipoles into trees with fishing rod, it works the exact opposite of fishing. Getting a line up 60'-80' into a tree is no issue.



Might have some issues matching the audio of the 2 units as well.

 

[towerdog]

Is a CB repeater possible? Yes. The frequency of use isn't the biggy.

Is a CB repeater practical? Not really. How do the users do that TX/RX off setting? And the really 'biggy', how do you get people to not interfere with it? I don't think there's a can big enough to hold all them worms!

Packet, or any other mode on CB? If it's AM or SSB based, it's certainly possible. Almost any mode can be 'produced' using a computer. The biggy is still going to be getting people to leave you alone while doing it (which says nothing about the legality of it). How about PSK31? Talk about a low power mode, that has got to be it. Same thing though, "Leave us alone!" just won't cut it I'm afraid.
- 'Doc

The idea behind it was not so much to extend range over open ground with hundreds of watts but to get around natural obstacles.

It does make a rats ass up here if it gets interference, cb is dead in this region, no interstate highway for 60 miles. Terrain is as rugged as it gets. What few users are on CB use it for comm., hunting, and socializing. none of this echo chamber, overmodulated, drunken lonely trucker splatterin across all 40 channels in a drunk monolouge braggin how much his amp puts out.

As for the FCC, i rofl, even if one of my fellow licenced amature radio operators turned me in for this, I am sure the FCC would rofl and the very idea of such a thing as a repeater on CB.

Its all just an expiriment anyway, if I ever do it, which the more people say it cant be done the more I want to do it. And I then again might never do it but I will have learned a great deal of knowledge researching and attempting too do it.

 

[towerdog]

Is a CB repeater practical? Not really. How do the users do that TX/RX off setting?

They don't. My hypothetical repeater will not work for users of newer PLL controled 40ch units, nor anybody elses unit that not modified.

It only be of use to older 23channel that use crystal mixing schemes.

one I am familar with uses 12 crystals, and there is a crystal somewhere in there for the TX refrence frequency, i think around 11Mhz, TX could be offset by changing value of this crystal. There were several schemes, I think one such you could simply rearrange crystal banks.

On the old realistic handheld 3ch and 5ch units, it used 2 pairs of crystal for each channel, so this would be easy to achieve an offset. Take the crystal pairs for ch.1 and ch.23, swap tx of ch 1 with tx of ch.23 and vise versa.

 

[Radio Tech]

I did this 25 years ago. Just for giggles. It was set at low power. Two seperate antennas. The repeater was made with two (2) seperate radios. As cheap as radios are no need to isolate one to make a repeater. The mobile unit is diferent although. This repeater was also on AM. So forget about a COR circuit or it will never unkey. I ran it for about 2 months just to see how it did. When the skip rolled in it would key for 10 minutes then time out.

It was fun, but not that usable.
I later built one using a GE Mastr II on 10 meters. Then later one on 2 meters.

 

[W5LZ]

Don't misunderstand, no one said it couldn't be done. It just isn't going to be easy, or very practical.
- 'Doc

 

[Radio Tech]

Don't misunderstand, no one said it couldn't be done. It just isn't going to be easy, or very practical.
- 'Doc

Easy? Yes
Practical? No

 

[SR385]

As for the FCC, i rofl, even if one of my fellow licenced amature radio operators turned me in for this, I am sure the FCC would rofl and the very idea of such a thing as a repeater on CB.

The FCC would be on you very very fast if you put up a repeater on the CB band. Putting a repeater on any frequency is no rocket science, just a matter of equipment.

The CB charter is so far from a service that would permit a repeater...it would be one of the fastest enforcement actions they ever acted on. I would bet on it.

The cavity filters are quite large for 27MHz, that would be the big annoying hurdle to deal with. Either that or you would have to use two linked locations for RX and TX.

 

[Captain Kilowatt]

I did this 25 years ago. Just for giggles. It was set at low power. Two seperate antennas. The repeater was made with two (2) seperate radios. As cheap as radios are no need to isolate one to make a repeater. The mobile unit is diferent although. This repeater was also on AM. So forget about a COR circuit or it will never unkey. I ran it for about 2 months just to see how it did. When the skip rolled in it would key for 10 minutes then time out.

It was fun, but not that usable.
I later built one using a GE Mastr II on 10 meters. Then later one on 2 meters.

Using two separate antennas is a start at isolation but generally is not enough to prevent desensing the RX. Running low power will help as well but to make a decent repeater with decent range you do need isolation because of the desensing problem when running any amount of power.