Radio Antenna Bases

[OPCOM]

actually there is a better way involving using the lowest frequency setting on the base and changing the value of a capacitor inside. The instructions are on the www somewhere, or were. The mast does not make a perfect match to the CB alone, it needs a matching network.

If you want a CB antenna with no fuss, use instead the HF whip antenna with 3 sections, and make the top section the short type.

Use the AB-652 base, and this is normally used with the MS-116-117-118 MAST SECTIONS - each 39.3"L.

Instead of this configuration, substitute an AB-21 - MAST SECTION, 27"L for the lower section, OR, substitute an AB-23 - MAST SECTION, 27"L for the top section. The result is two 39.3" sections and one 27" section, so that the total length in conjuction with the AB-652, makes a very good match for the CB. In any case a hose clamp or other means is used at the base of the antenna to ground the shield of the coax cable.

 

[tennmogger]

I agree wholeheartedly with OPCOM, it's better to use the MS and/or AB-series whips with a simple base like the AB-652 or AB-15, to put on CB. Just aim for a 102" length, including the whippy/spring section of the base. I use this configuration in my 1965 Unimog 404 radio comm truck and it works well on CB, plus 20, 15, 17, and 10 meters. For you hams out there, a 50 ft horizontal wire clipped to the AB-15 base (along with the whip) can make a good NVIS antenna for 80 and 40 meters too (fed with a tuner, I use the military RF Communications RF-302).

It's such a waste of a AS-1729 to gut it. Also, the whip antenna (AS-1720 and AT-1095) is a center-fed dipole configuration, the reason the complicated matching network is required in the base. That whip isn't a simple base fed quarter wave as it looks it should be and presents a completely different feed point impedance.

Bob

 

[jakwi]

OPCOM,

I was wondering if you have any ideas on where that website might be. I've been googling all morning. and I haven't had any luck. My recently aquired antenna base is a AS-3900. I'd like to shift the frequency range down into HF for ham use.

any help would be greatly appreciated.

thanks!

actually there is a better way involving using the lowest frequency setting on the base and changing the value of a capacitor inside. The instructions are on the www somewhere, or were. The mast does not make a perfect match to the CB alone, it needs a matching network.

If you want a CB antenna with no fuss, use instead the HF whip antenna with 3 sections, and make the top section the short type.

Use the AB-652 base, and this is normally used with the MS-116-117-118 MAST SECTIONS - each 39.3"L.

Instead of this configuration, substitute an AB-21 - MAST SECTION, 27"L for the lower section, OR, substitute an AB-23 - MAST SECTION, 27"L for the top section. The result is two 39.3" sections and one 27" section, so that the total length in conjuction with the AB-652, makes a very good match for the CB. In any case a hose clamp or other means is used at the base of the antenna to ground the shield of the coax cable.

 

[mistaken1]

OPCOM,

I was wondering if you have any ideas on where that website might be. I've been googling all morning. and I haven't had any luck. My recently aquired antenna base is a AS-3900. I'd like to shift the frequency range down into HF for ham use.

any help would be greatly appreciated.

thanks!

I do not think you can do that with a 3900, at least not without changing hardware.

Here is the link I believe you are looking for:
Military Antenna Conversion for CB

I bought an MX-6707 complete off epay and did this modification. It works. Although I am going to remove the CB and use a 6-meter radio so I will use the same procedure to tune one of the other switch settings to work at 6-meters.

 

[Brentzilla]

I see that you can NOT use the AS-3900 for ham radio use, but what about CB? I read on one site that you can but only to about 100 feet. I acquired myself a brand new in box AS-3900 with the whip, one AS-3900 w/o the whip, and one mount. I guess worst case maybe I can trade them for an antenna that will work with a CB.

 

[popacom]

I had occasion to do some testing of both antenna's the AS-3900 and the AS-1729 connected to
an RT-524 (VRC-12) radio and they both will work as they both cover basically the same frequency range. The AS-1729 has matching coils which as the radio is tuned a servo set up in the base
mechanically switches to match to the frequency in use. The AS-3900 is a "WIDE BAND" arrangement which simply put means it WILL work across the specified band but will not offer as close of a match on specific frequencies as the AS-1729. The AS-3916 was developed for use
in high impulse/backblast configurations such as self propelled guns,tanks etc. and is also a
"WIDE BAND" type antenna which is also on the same frequency range.
The biggest problem I see with using the AS-3900 or AS-3916 is that since they are not as
precise of a frequency match with the VRC series radio's you tend to see a lot of reflected power sent back to the radio. As long as this is not "TOOO GREAT" no big deal but if the match is way off
you could damage the radio when in the HIGH pwr. setting. I have used them with good success but I frequently check SWR and reflected pwr. to verify all is well. Just my .

Thanks!!! popacom / BILL in Ky.

 

[Brentzilla]

I had to look up what SWR was and found a good site:
Measuring SWR

So I should get a SWR tester, hook it up and see if my reading is above 2:1 which is bad

 

[Rich Johnson]

There are alot of surplus antennas out there. Basically, if the antenna states that it is for the 30-88 MHz band than it will do just that. 6m Ham band included.
There is an even broader antenna that is used for the PRC-117 vehicular installation and is becoming more prevalant. It is ranged from 30-512 MHz. Talk about versatility. Though a SWR check is necessary to verify its match before you use a ham radio with it.

I have often wondered if the AS-3900 or its immediate predecessor (3684 I think) would work on a CB. I have never tried it. An SWR meeter would be all that is necessary, but I do not have a CB any more.

If you want a military antenna for a CB as previously stated, there is also a very good base for use with the MS elements. Its better than the old AB-15 brown porcalin insulated unit. I cant remember the number, but it is for the PRC-104 on the GRC-213 vehicle mount. Its rubber insulated and has an N connector on the bottom. Find online where it shows how many MS elements are necessary for a vehicle whip for use with a PRC-8. Then get an SWR meter and check it.
Another thing you can do is go here N3DNO's Antenna calculator
and use the bottom calculator for a verticle and use the 1/4 wave figure.
If you only use one CB channel most of the time, use the frequency from this chart as your guide CB band frequency chart

 

[M37B1 1965]

Hi,

I found a dealer in Germany selling the MX2799 matching unit if your still looking for them.

 

[M37B1 1965]

Hi,

I'm currently looking for the mount for the MX2799 used on the M37 and M35 during the the 1960's,i'm interested in any parts however small,so far ive not had any luck,there was some one on the G503 web site said he had some back a few years,and i tried to register to there site with no reply...
I live in hope...
Thanks in advance.

 

[raeme]

Can anyone HELP? In Australia we use 40 ch UHF for mobile comms. Could somebody come up with a sugar scoop base and 3-piece antenna and base of the 70s issue on vehicles? If so please contact e-mail bluebell21@optusnet.com.au
raeme.