[R-390] antennas

[Mark Huss]

Bob, If you run over to Yahoo Groups, Shortwave-SWL-Antenna, there has 
been an interesting conversation on this very subject under the subject 
'Antenna Tuners' and 'Not Sure Why' that has been going on now for about 
a week. Lot of good stuff about the value of matching impedances, or 
not, in receiving antennas.

Bob Camp wrote:
> Hi
>
> You can go *very* crazy trying to match a random wire antenna. 
> Guessing it's impedance is tough because of all the variables. Best 
> bet is to try a couple of ideas and go with what worked best. You 
> probably will find that what works best at some frequencies works 
> poorly at other frequencies.
>
> The best way to feed a 390A is with balanced coax. That's only true if 
> you feed the coax from a balanced source. Since you want high 
> impedance, you need both a "choke" balun and a matching transformer. I 
> have had pretty good luck with doubled small diameter coax wound on 2" 
> EMI cores for the chokes. Yellow or red iron cores work okl for the 
> matching transformer if you get up above 1 1/2" diameter. Stick with 
> teflon insulated wire / twisted for the windings of the transformer 
> section.
>
> Bob
> KB8TQ
>
> On Oct 17, 2007, at 9:31 AM, Rasputin Novgorod wrote:
>
>> Hi Guys:
>>
>> My random wire connects via a 9:1 un-balun to 50 ohm coax.
>> The shield is grounded. Because I had the correct adaptor,
>> I connected the coax to "Unbalanced" antenna connector on
>> the R-390A. It works well.
>>
>> But as I skim the schematics, it appears that the unbalanced
>> antenna connector goes to the secondary side of the input
>> preselector(?) CL filters. Does that mean I miss out in the
>> first layer of filtering?
>>
>> The "Balanced" connection goes to the Primary side the
>> "preselector". Would I be better off connecting there?
>> I know some people connect an unbalanced antenna to the left
>> pin of the "balanced" connector and ground the right pin.
>>
>> In the good old days, how would the military connect the
>> Balanced connector to a dipole? Would they have some
>> sort of 125 ohm dual conductor coax? Surely not
>> ladderline.
>>
>> Perhaps instead of answering my questions, someone can tell
>> me what I need to know...
>>
>> Sincerely,
>> /blair
>>
>>
>>
>> __________________________________________________
>> Do You Yahoo!?
>> Tired of spam? Yahoo! Mail has the best spam protection around
>> http://mail.yahoo.com
>> _____________________________________________________________
>> R-390 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>> Help: http://mailman.qth.net/faq.htm
>> Post: mailto:R-390 at mailman.qth.net
>> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>>
>
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>


-- 
----------------------------------------------------------------------
Some people are like a Slinky .. not really good for anything,
but you still can’t help but smile when you shove them down the stairs.
----------------------------------------------------------------------