Page 1 of 2 1 2 LastLast
Results 1 to 10 of 12

Thread: How To Modify A Military Antenna Base For CB Use (pics)

  1. #1
    Private
    Join Date
    Feb 2015
    Location
    Florida
    Posts
    1
    Thanks
    0
    Thanked 30 Times in 1 Post

    Tech How To Modify A Military Antenna Base For CB Use (pics)

    I have recently been working on modifying military antenna bases for CB and had a friend asking how and asking me to "show" it here. After looking over this site I’ve seen a lot of posts asking about using military bases for CB radios and 10 meter export radios. Most of the answers in these posts are “yes you can”… followed by no other information… or… helpful but wordy which is hard to follow if you are messing with something beyond ones normal comfort zone. Some is just poorly thought out to the limitations of “Average Joe’s” (non-radio guys) understanding. Or… actually snide and downright wrong with the arrogant intent of frustrating anyone without a HAM background.

    So here's one with pictures...

    If there is one there are 100 different surplus bases out there none of them to my knowledge that will work for 11 meter (CB radio). The base I am going to direct you to an AN-3916VRC which was developed for the military after they figured out that vehicle fired rockets tend to melt sectional antennas. It is a very cheap base, usually selling for $20-$30 dollars ($40 if you are lazy on Ebay). It uses a plan ole SS whip antenna that can be purchased just about anywhere for $25 and once built can be tuned (SWR) like any other CB whip antenna. The base comes with a BNC connector that can be used “as is” or you can easily swap it out for a PL-259 connector (standard CB coax connector). They dissemble easily and only need basic modification to work like an off the shelf “CB antenna”. Best of all when you are done with it you have a true ¼ wave whip which is about the best mobile antenna one can have and for only about $70.


    Tools Required

    Basic soldering stuff… Iron, solder, a solder sucker helps but is not required.
    Basic hand tools
    A number 7 drill bit and hand drill.

    If you are changing out the BNC connector for a PL-259 you will also need…
    A 5/8 drill bit
    Round file


    Materials Required
    AN-3916 base $20-$40
    102” (sometimes 103”) SS whip antenna $18-$30
    Random piece of 18ga wire (maybe, maybe not)
    Silicone
    Larsen Whip tip for a W490 & W450 PN “Ball1” (they sell these on Ebay for $10 each, a bag of 10 is under $7 online if you search for them)

    If you are changing the connector

    Female chassis mounted PL-259 connector. (google it) $5 and worth doing.

    7.jpg

    A few notes on materials and methods…


    When buying the AN-3916VRC, if it is missing the Jam Nut from the top… DO NOT BUY IT! They are almost impossible to find on any consistent basis.

    1.jpg

    The Larsen Ball1 whip tip is not a “suggestion”… Whips put out eyeballs! Don’t be the douche that sticks a 100+ inch antenna on to his truck and blinds someone!!!!

    BALL2B.jpg

    What we’re doing here is “unloading” this antenna base which is currently tuned for 6 meter military frequencies. In laymen’s terms… were gutting it and bypassing all of the fancies making the coaxial core go straight though the base and into the whip.


    As someone(s) will inevitably point out…


    You could unload this base by simply jumping from one side to the other, however the proposed method leaves you room to go backwards later or repurpose the base by reloading it for other uses. It also preserves the ability to split the base into 2 halves for easy working. You can stick a whip on the base “as is” and probably trim it to work within proper tuning… It would however be a VERY short (worthless) antenna.




    Doing The Deed

    Dont fret, were actually going to rip out and destroy every internal part while only changing 2 things!


    2.jpg

    1. Mounting the base upside down in a vice and remove the 8 stainless steel Philips head screws around the outside and gently pry upwards on the base bottom exposing the insides.

    3.jpg

    2. Put the base bottom section in the vise and remove the three #8 screws and one #4 screw as shown. This will allow you to pull out the coil plate and expose the back side of the BNC connector.

    4.jpg

    If you are not changing the BNC connector unsolder the wire shown and skip to step 7

    5.jpg

    3. Unsolder the white wire shown at the back of the BNC connector.
    4. Using a 5/8 socket remove the connector from the base.
    5. Use a 5/8 drill bit to enlarge the connector hole.
    6. Use a file for final fitting in install your new PL-259 connector.

    6.jpg

    7. Cut the resistor leads as shown in the picture

    8.jpg

    8. Solder the white wire (some are too short to move and must be replaced, use 18ga primary wire) to the screw base as shown. Set the antenna bottom off to the side, that part is finished.

    9.jpg

    9. Turning your attention to the coil plate, note the parts to cut and unsolder in the photo. You are basically disconnecting all pathways on the coil plate from each other.

    10.jpg
    10. Install a jumper wire to bridge as shown. (A piece of one of the removed coils works well for this once you burn off the red coating.)

    11.jpg

    11. Reinstall the now coil(less) plate back into the antennas bottom section. DO NOT OVERTIGHTEN THESE SCREWS!!!!

    12.jpg

    12. Apply a SMALL amount of silicone to the edge of the antennas top section as shown. (Unless you are still active military, then apply the whole **** tube to it.)
    13. Reassemble the top and bottom halves, reinstalling the 8 screws taken out in step one. Again… DO NOT OVERTIGHTEN THESE!
    14. Clean off any excess silicone. (unless active military, if so, just leave it all over for the next guy)

    13.jpg

    15. Turn you attention to the jamb nut on top of the base. The ID of this is slightly smaller (.200) than needed for the new whip (roughly .220) to fit into. Using the number 7 drill bit, enlarge this hole with the jam nut installed (hand tight) in the top as shown.

    If you do not drill the nut in the base as shown the bottom section will expand on the bit and not remove enough material when drilling.

    14.jpg


    16. Cut the threaded portion of the SS whip antenna off, file the edges, install into your newly modified base.

    16.jpg

    17. Install and tune following the instructions below…

    Notes on vehicle mounting locations

    If you have the opportunity to mount the base in a forward position on the vehicle so you antenna(s) tie to the rear do it. This helps prevent folding the antenna forward which will eventually get snagged on something and destroy it… Watching the whole event unfold in front of your eyes is about the only positive thing I can think of for rear mounting. Mid vehicle mounting with at least 70% of the antenna above the vehicle will usually perform better than corner mounting.



    Stolen, entirely from Right Channel Radio


    1. The first thing you need to do is find a suitable location to park your vehicle. There should be no obstructions, such as trees or buildings, within 10 to 15 meters of your antenna. Neither you nor your buddies should be hanging out around the car, either. Make sure that you’re inside with the doors and windows closed to ensure an accurate reading.
    2. The next step is to hook up the SWR meter. First, disconnect the coaxial cable from the back of the radio. Reconnect this end of the cable, which is going to the antenna, to the SWR meter in the connector marked “antenna” or “ANT.” Next, use the jumper lead to connect your radio and the SWR meter through the connection marked “transmitter” or “XMIT.”
    3. Now you are ready to measure the SWR on a few different channels. Remember, throughout this process it's important to keep the microphone the same distance from the meter for each test.
    4. Set the switch on the SWR meter to “FWD.”
    5. Turn the radio to channel 1.
    6. Key the microphone (depress the button and hold it).
    7. Turn the knob on the SWR meter labeled “SET” or “ADJUST” until the needle reaches the setting position at the end of its range.
    8. While still keying the microphone, flip the switch on the SWR meter to the “REF” or “SWR” position.
    9. Quickly record the reading given by your SWR meter and release the transmit key on your microphone.
    10. You are now going to repeat this process for channel 40. Follow steps 4 through 9.

    The objective behind tuning your antenna is to make these two readings as close as possible. Getting down to a 1.5:1 ratio or below makes for a passable broadcast signal. There are two basic points to understand before adjusting the length of your antenna:

    • If the SWR on channel 40 is higher than that on channel 1, your antenna is too long.
    • If the SWR on channel 1 is higher than that on channel 40, your antenna is too short.

    If your antenna is too long, it is necessary to reduce its physical length. There are several methods for shortening an antenna which vary by manufacturer. Consult your owner’s manual for detailed instructions on how to shorten your antenna. While many antennas feature a “tunable tip” that uses a small screw, some antennas may need to be cut to be shortened. Do so in 1/4" increments and then get new readings to determine your progress.
    If your antenna is too short, it is necessary to increase its physical length. Most instances where the antenna length is too short are caused by a lack of ground plane. In modern antennas, there's usually a method for adding length built in to the antenna.
    End of stolen materials…

    There should be no issues with being too short when using a 102” whip. If however… for some reason… somehow… you find this to be the case, remove the spring section from the top of the base and change the shielded wire inside the spring out to a longer unshielded insulated wire such as automotive 14ga primary wire and retune.

    Hopefully this helps a few people out and who knows, if the mod takes off maybe we’ll see it become the “Dog Head CB antenna mod”.
    Attached Images Attached Images

  2. The Following 30 Users Say Thank You to The Name Is Fred For This Useful Post:

    146APF (02-25-2015), 85 USMC M998 (04-27-2017), Bill W (07-31-2016), Boats (06-23-2017), Bobcat701 (06-30-2016), cbear (02-26-2015), ClarkeF (08-26-2015), clinto (02-24-2015), cucvmule (09-11-2017), firefinder (08-12-2018), Glockfan (12-02-2016), GMVguy (09-15-2015), gtodan (04-27-2017), hahn84 (09-18-2019), JonMolander (03-23-2015), Lizard Dog (07-09-2016), M813rc (04-05-2015), MR3C (03-21-2016), MtnSnow (04-05-2015), muddog (02-20-2017), nchittendon (02-27-2015), orgnal (07-28-2016), Royalpower (07-28-2016), SCSG-G4 (02-25-2015), Stephenfloyd (09-22-2016), Storm 51 (07-29-2016), T. Highway (02-26-2015), timarr (08-30-2015), Whiterabbit (02-25-2015), zebedee (02-24-2015)

  3. #2
    LLM/Member 785 Recovry4x4's Avatar
    Join Date
    Jun 2004
    Location
    GA Mountains
    Posts
    33,399
    Thanks
    757
    Thanked 10,284 Times in 4,616 Posts

    Default

    Would it work with a 3910 base as well?
    1986 M1008
    1984 M1031
    1984 M1010

  4. #3
    4 Star General Stonepicker1's Avatar
    Join Date
    Nov 2008
    Location
    Coconut Creek, Florida
    Posts
    2,419
    Thanks
    892
    Thanked 764 Times in 408 Posts

    Default

    opcorn:
    Phil
    CSM 88M60/63Z60 /63B/52D

    1984 M1009
    1986 Chevy M1031 into M1028A1 in 1992
    1986 Chevy M1028A2 Dually(New 6.5L GEP engine w/Banks Turbo)
    1986 Chevy M1028A2 Dually, 6.2L
    1991 MEP-003, 10 KW Gen
    1999 CUCV-II 6.5L Turbo(New 6.5 GEP engine)
    2000 CUCV-II 6.5L Turbo
    2000 CUCV-II CREW CAB, 6.5L Turbo
    2000 CUCV-II CREW CAB, 6.5L Turbo
    2000 CUCV-II Dually, 6.5L Turbo
    2001 M-Gator 6X4
    2005 LSSV Chevy 2500 4x4, CREW CAB, 6.6L Duramax
    2006 PU-405, 30KW Gen
    2006 M116A3 1 ton Gen Trl
    2009 A1 M-Gator 6X4
    19?? 4K RT, 4000 lb Forklift(SeeBee)

    VFW Life Member (Hillsdale, Mich)
    PJSArmory.com

  5. #4
    2 Star General Whiterabbit's Avatar
    Join Date
    Feb 2009
    Location
    Erwin Tn.
    Posts
    742
    Thanks
    255
    Thanked 373 Times in 191 Posts

    Default

    Nice how to!
    BTW it's a AS-3916 VHF antenna.

    Abandon all hope! It'll make you focus better!

    Give a man a fire, he's warm for a day. Light a man on fire, he's warm for the rest of his life!

    1986-2014 Ordnance Corps RETIRED!
    1978 ex MOD Land Rover 109 Series III
    42 WLA in bits 'n pieces
    1972 uncut M151A2 with 1966 M762 1/4tn trl.
    1994 DNEPR MT-16

    Sent with smoke and mirrors.

  6. #5
    Sergeant Lizard Dog's Avatar
    Join Date
    Oct 2014
    Location
    Los Angeles
    Posts
    72
    Thanks
    153
    Thanked 61 Times in 27 Posts

    Default

    Great write up! May I ask where you're finding these antenna bases for $40? I'm only finding them around $200
    1986 M1009
    6.2L with Banks Turbo
    TH400 w/ Derale Hyper-Cooler and Rostra cruise-control
    NP241
    Dana 60 front & GM14-bolt w/ G80; 4.10 gears
    37" Goodyear MT/OZ on HMMWV 8-bolts
    Offroad Design 3.5" lift springs front w/ axle offset plate (1" fwd)
    ORD 4" shackle-flip rear w/ ORD Zero Rates (1"back)

  7. #6
    Sergeant Boelt63A's Avatar
    Join Date
    Jul 2006
    Location
    Jacksonville Florida
    Posts
    77
    Thanks
    3
    Thanked 2 Times in 1 Post

    Default

    When this was written last year they had been very plentiful. I bought 4 for my trucks and this mod has worked very well. Times change, when I started in this hobby, Deuces routinely sold for $500 after a depot level refurb.
    1987 SOCOM Pinzgauer 718
    1976 Pinzgauer 712M
    1974 Pinzgauer 710M -wrecked 2008 . (sold for parts 2012)
    KF4ZAN

  8. The Following 2 Users Say Thank You to Boelt63A For This Useful Post:

    Lizard Dog (07-29-2016), nchittendon (07-30-2016)

  9. #7
    General dougco1's Avatar
    Join Date
    Oct 2011
    Location
    Cooperstown NY
    Posts
    488
    Thanks
    707
    Thanked 310 Times in 175 Posts

    Default

    That is a lot of work for to convert to a CB. I use a working MX 6707 base with the 1730 mast. All you have to do is cut the upper section of the mast shorter (12-16") and manually tune the knob on the bottom of the base till you gain reception. It works fine for 2-3 miles out even with the antenna tied back. And you also get great radio skip on certain channels for more listening pleasure.

  10. #8
    Private
    Join Date
    Aug 2016
    Location
    Bechtelsville, PA
    Posts
    1
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    First and foremost, thank you for taking all the time you did to write the article and to post the pictures.

    Second, I am trying to determine whether I can re-purpose a military antenna for AM/FM use. I noticed your section on tuning the antenna for those wishing to utilize it for CB but I'm not sure how (or if) it can be tuned for AM/FM use. It would seem to me that if it can be re-purposed for AM/FM, it should be substantially better than a stock AM/FM antenna. Thanks for any guidance

  11. #9
    Private
    Join Date
    Sep 2016
    Location
    Lancaster, PA
    Posts
    1
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    I would like to use the full antenna, not just the base. I want the Mil spec look, and well I already own the whole thing so, why not? If I modify the base as listed above, would I be able to use my whole unit?

  12. #10
    2 Star General
    Join Date
    Jul 2017
    Location
    Crystal City Mo
    Posts
    725
    Thanks
    1,803
    Thanked 637 Times in 333 Posts

    Default

    Tag I am going to try this.
    Belt Fed Multi Barrel Motor Motivated

    Help From Above

    GAU 8 See You Next Time

Page 1 of 2 1 2 LastLast

Similar Threads

  1. Anyone use the MX6707 base and military whip antenna for 2 Meters?
    By MarkM in forum Military Radios and Other Electronics
    Replies: 2
    Last Post: 10-02-2014, 15:37
  2. Replies: 16
    Last Post: 07-03-2012, 11:55
  3. military spring antenna base for 2-meter operation
    By maddawg308 in forum Military Radios and Other Electronics
    Replies: 6
    Last Post: 01-07-2012, 00:37
  4. M1009 Antenna and Antenna Base
    By donalloy1 in forum CUCV
    Replies: 10
    Last Post: 10-14-2010, 14:34

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •