[R-390] Proper Ant Connection for an R-390a

[Mack McCormick]

Roy,

Thank you for a very detailed explanation of options. I'll probably still
with the method I'm using now since it seems to work great. Again, I really
appreciate you taking the time to reply. I'll try to contribute to the
group as I can.

73,

Mack
W4AX


On Mon, Nov 12, 2012 at 8:20 PM, Roy Morgan <k1lky at earthlink.net> wrote:

>
> On Nov 12, 2012, at 1:42 PM, Mack McCormick wrote:
>
>  My R-390a restoration is complete and working great!
>>
>> Here are some pictures
>>
>
> Mack,
>
> WOW!  You have done a superb job on that radio.. congratulations.  It's an
> inspiration.
>
>  ... how should a typical ham antenna be connected to the receiver?
>>
>
> Simple way: ground one twinax pin and feed the other one with your coax,
> as you seem to be doing now.
>
> The NAVships re-arrangement simply accomplishes the simple way above by
> moving the connections around in the radio and modifying a UG adapter so
> you can use the single type C connector for convenience (and so as to not
> damage the antenna relay and adapter.)
>
> Expensive way: spend $30 or more for the UG-970 or -971 adapter which does
> the same thing.
>
> Homebrewed way:  cobble up a bit of coax, a female SO-259 wire mount
> connector and a twinax connector to do the same thing.
>
> Really nice home brewed way: get a nice twinax connector, and a female
> single hole chassis mount  connector - or preferably a right angle one, buy
> a 5/16 X 24 tap*, thread the twinax connector  clamp bushing for the BNC
> threads, and assemble the thing with with a couple bits of wire.  (I did
> this - very nice since most/all of my receive and low power coax is BNC
> terminated.)
> *This may not be the correct thread specification, do check it if you
> decide to do this.
>
> Improved home brewed way: do the above but include a small ferrite toroid
> selected for the HF spectrum and wound to match the 50 ohm coax to the
> nominal 125 ohm balanced input.  (I have not done this, but would like to
> to see if it makes any difference.)
>
> More complicated way:  Run your balanced line all the way to the rear of
> the radio, use both twinax pins.
>
> Slightly more complicated way:  buy or scrounge a fairly modern TV type
> receiving balun, feed the twinlead end to the balanced connector and your
> 50 ohm coax to the type F end. One fellow claims this makes a significant
> improvement on older radios meant for balanced antenna setups.
>
> Similarly more complicated way: rework your 4:1 balun to match the
> balanced line to 125 ohms.  Use the twinax connector.
>
> Yet more complicated way: find and use some twin conductor coax (not so
> easy to find now) with 125 ohm impedance and make some sort of impedance
> transformer or network to match the balanced line you have to the twin coax.
>
> Finally, do report what you do and how it works!
>
> Roy
>
> Roy Morgan
> k1lky at earthlink.net
> K1LKY Since 1958 - Keep 'em Glowing!
>
>
>
>


-- 
73,

Mack de W4AX
http://w4ax.com