AS-1729/VRC for CB Band

[TJ4man]

All -

Very new to this, and this forum has been a wealth of knowledge so far.

My original intention was to take an MX-6707 base and AS-1729 antenna set to mate with a CB. This would maintain the correct 'look' of the M934A1, and be functional. I have been reading up on this for a bit (thanks to this forum and others) and found the following information interesting (link below).

I have read of some 'gutting' the MX-6707 and just connect directly with the coax, but this article suggests it's possible to set the lowest band (30-33MHz) to the CB band (27MHz), by verifying the adjustments with an SWR meter.

Anyone tried this?

AS-1729/VRC - RadioNerds

radionerds.com

TJ

 

[papakb]

What you've read is correct. The advantage of using an MX-6707 for your antenna beyond it's appearance is it's tunable base. I would definitely recommend against gutting it because good units are getting harder to find and it's a great military antenna to use with lots of radios.

My recommendation would be to get an SWR (or VSWR) meter and then tune the base so that you have the best forward to reflected power ratio with your CB and then leave it there. These antennas ares designed to tune from 30 - 75 Mhz and even though the CB frequency range is down at 27 Mhz there will be places where the you'll get an acceptable match.

Antenna matching is the tuning of the antenna with a radio set so that you get the highest transmitted power out with the least (wasted) power reflected back into the transmitter. Most CB radios are meant to handle bad antenna matches so your not going to hurt the radio with a tiny bit more reflected power and your obviously not looking for DX (long range) communications by the nature of your wanting to use a CB radio since that's not what they were designed for.

 

[TJ4man]

Papakb, thanks for the reply... sounds like I am on the right path. I was able to find and purchase a pair of MX-6707 bases, one of which I will use for the CB application. Now on the hunt for an AS-1729 set (and SWR meter) to mate up and tune. I just got the truck, so the project list is long!

Thanks,

TJ

 

[papakb]

The antenna masts are fairly inexpensive but a PITA to ship!!

 

[Overboard]

Hoping to fire this thread back up but I have the same intentions, I have both 6707 base and antenna however i have never having delt with radios before so, was it successful and any tips or further information than the link can provide. Maybe pics of steps more of a visual learner.

Also if just using for cb how do you power up the base.

 

[SCSG-G4]

Hoping to fire this thread back up but I have the same intentions, I have both 6707 base and antenna however i have never having delt with radios before so, was it successful and any tips or further information than the link can provide. Maybe pics of steps more of a visual learner.

Also if just using for cb how do you power up the base.

The base has the antenna coax straight from the radio - the SWR meter goes in that line. The other cable is strictly for changing the frequency range from the radio itself, but that can also be done with the base itself, mechanically. Once set for the lowest SWR, you simply leave it alone, and you do not need the control cable.

 

[Overboard]

The base has the antenna coax straight from the radio - the SWR meter goes in that line. The other cable is strictly for changing the frequency range from the radio itself, but that can also be done with the base itself, mechanically. Once set for the lowest SWR, you simply leave it alone, and you do not need the control cable.

Do i need to power the base?

 

[cagosti]

No

 

[SCSG-G4]

No

Correct, the only 'power' is the radio signal that you will be transmitting through the coax. The other cable did transmit power to the stepper motor to change the SWR for different frequency ranges in the 30-75 MHz range. You will not be doing that, because the frequency range that you will be working on is MUCH narrower, and one setting will do for all the channels that you can use.

 

[papakb]

See this old posting: https://www.steelsoldiers.com/threads/radio-question-from-newb.104797/#post-1333907

 

[Overboard]

Correct, the only 'power' is the radio signal that you will be transmitting through the coax. The other cable did transmit power to the stepper motor to change the SWR for different frequency ranges in the 30-75 MHz range. You will not be doing that, because the frequency range that you will be working on is MUCH narrower, and one setting will do for all the channels that you can use.

Will i have to take this apart like i have read on other sights are will the SWR meter adjust it?

 

[papakb]

All you need to do is to put the SWR meter in series with the BNC cable to the antenna base and then turn the frequency knob until you get the best antenna match. ie, When the SWR is the lowest. There's no need to disassembly anything.

 

[Overboard]

All you need to do is to put the SWR meter in series with the BNC cable to the antenna base and then turn the frequency knob until you get the best antenna match. ie, When the SWR is the lowest. There's no need to disassembly anything.

awesome thanks

 

[chucky]

The base has the antenna coax straight from the radio - the SWR meter goes in that line. The other cable is strictly for changing the frequency range from the radio itself, but that can also be done with the base itself, mechanically. Once set for the lowest SWR, you simply leave it alone, and you do not need the control cable.

I ve got a AS-3900 base an what ever that fits on it as a antenna (2 piece ) and is there any way to make it into a useable cb/10 meter antenna all this is mounted on pass side scoop mount and i just mounted the dr side mount on the truck so i have another way to go if this 3900 base doesnt work !

 

[SCSG-G4]

I ve got a AS-3900 base an what ever that fits on it as a antenna (2 piece ) and is there any way to make it into a useable cb/10 meter antenna all this is mounted on pass side scoop mount and i just mounted the dr side mount on the truck so i have another way to go if this 3900 base doesnt work !

I have not dealt with the AS-3900 base, BUT, you should be able to put an SWR meter inline between the radio and the base and see if it can be adjusted for the frequency you are using. SWR - Standing Wave Ratio see this site for more information > https://www.maximintegrated.com/en/glossary/definitions.mvp/term/SWR/gpk/815

 

[papakb]

Hi Mike, The AS-3900 isn't adjustable as far as the frequency is concerned like the AS-1729 and I've never swept one to see exactly what the range is but the VSWR meter should give you a clue as to whether or not the 3900 will work with a CB set on 27 Mhz. Do people still even use the Citizens Band? I haven't turned one of my radios on in a decade or so!

 

[SCSG-G4]

Hi Mike, The AS-3900 isn't adjustable as far as the frequency is concerned like the AS-1729 and I've never swept one to see exactly what the range is but the VSWR meter should give you a clue as to whether or not the 3900 will work with a CB set on 27 Mhz. Do people still even use the Citizens Band? I haven't turned one of my radios on in a decade or so!

I have not had an operational CB in over 30 years! You are correct about the AS-3900, it is 'supposed to be' close enough for military use in the entire spectrum they are using. Modern US military radios use frequency hopping extensively as a security measure.

 

[chucky]

Hi Mike, The AS-3900 isn't adjustable as far as the frequency is concerned like the AS-1729 and I've never swept one to see exactly what the range is but the VSWR meter should give you a clue as to whether or not the 3900 will work with a CB set on 27 Mhz. Do people still even use the Citizens Band? I haven't turned one of my radios on in a decade or so!

Im not sure if anyone that does use a mobil cb will be found between 1 and ch 40 but everyday/night use in the touring entertainment industry between semis and busses they just stay off in the middle of nowhere on the freq band where its quiet and for the most part no one on the road can come find us or listen , Everybody had to have freq counters so you knew where to go to find everyone on your tour and half the time spliting channels by 10kzs . Some of the guys likes to shoot skip early in the morning if it was running where you were at and alot of us were running RANGER RCI 63FFC4 's and could really get spread out over 20 to 30 miles apart at night and still talk to one another so it kept us awake at night and entertained ! And on the 3900 if i can start getting close on swr 's do you start grinding the end of the antenna a little at a time like we do stainless whips to get down to 1.5 or do they not do that with these military antennas?

 

[SCSG-G4]

Grinding on the end is likely to damage more than it fixes. It's not 'just' a piece of metal. If I remember correctly the antennas are more like an array of different lengths (electrically) and the transmit signal goes up the path of least resistance. That 'least resistance' may still be a 2-5 or worse SWR, but most battlefield radio communications is done over less than 2 miles. They have different stuff for longer ranges (both radios and antennas).

 

[chucky]

Grinding on the end is likely to damage more than it fixes. It's not 'just' a piece of metal. If I remember correctly the antennas are more like an array of different lengths (electrically) and the transmit signal goes up the path of least resistance. That 'least resistance' may still be a 2-5 or worse SWR, but most battlefield radio communications is done over less than 2 miles. They have different stuff for longer ranges (both radios and antennas).

OK so on the military stuff they either have a in-line tuner to get the swr's down instead of triming the antenna ive always tried to go for a 1,0 but settle for a 1.5 but not let it go higher even if i had to use other coax or antennas , Thanks