[MRCA] Commo #4 MX-6707

[scottjohnson1 at cox.net]

All-

I was able to purchase two NOS in box MX-2799s with whips and all mounting accessories recently for $50 at the Phoenix MV show.  Most people don’t know what they are and pass them by!

I had thought they were used exclusively on armored vehicles, but I guess they pre-date the AS-1729.  Anyway, the units I purchased were manufactured in 1986.  Looks like it belongs on my  M-715.  Probably a bit much for a poor little MUTT!

 

Scott W7SVJ

 

From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> On Behalf Of Tim
Sent: Wednesday, June 5, 2024 16:51
To: MilComm Guy <m38inmaine at gmail.com>
Cc: MRCA at mailman.qth.net
Subject: Re: [MRCA] Commo #4 MX-6707

 

Hi Mark - Nice installation!  I was unaware of the "shoebox" variant for these antenna matching units.  Just the MX-6707/VRC types usually seen.  Here is what I have learned about the AS-1729/VRC system and how I have used it if you're bored:

https://www.n6cc.com/as-1729-vrc-vhf-whip-antenna/

Thanks for the link to the Army's failure modes study. Significant issues with water intrusion, big project to address it.  Lots of them fielded!

Tim

N6CC

 

On Wed, Jun 5, 2024 at 3:53 PM MilComm Guy <m38inmaine at gmail.com <mailto:m38inmaine at gmail.com> > wrote:

I received a comment about the high failure rate of the round tuning units and he is correct, the military did a study on how to try and correct this.

 

https://apps.dtic.mil/sti/tr/pdf/ADA118281.pdf

 

Leaving the antenna tied down opens the spring coils and allows water in, also the plastic version develops cracks where water can get in.  When looking to buy one check for cracks and make sure the manual tuning knob on the bottom turns freely, if not pass on it.  

 

The MX-2799 tuning unit has the spring base mounted separate from the tuning unit allowing more flexibility of where you can mount the tuner and still have the antenna vertical and no chance of water entry from a tied down antenna.





 

Mark

K1HF

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