[R-390] R-390A help needed

[Larry Haney]

Hi Karsten,  Welcome to our reflector list.

Using a 'balun' on the front end to match the impedance of a 50 ohm
splitter or antenna to the twinax balanced antenna input on the 390 is not
necessary and is a detriment to use.  The 390 balanced input works great on
50 to 200 ohm feeds.  And, the balun is a lossy device and at low signal
levels is going to show up as weak signals appearing even weaker.  You
might think that having a balanced impedance on the input is beneficial,
but the loss in best 'balun' is much higher than any gain from the
balanced impedance.  There have been numerous posts on our reflector on
this subject.

If you want to do the alignment, there are numerous folks on our list
willing to assist you on that and any other problem you might have.  Have
fun.

Regards, Larry (I'll be 84 in April)

On Sat, Feb 8, 2025 at 7:32 AM Karsten Simon via R-390 <
r-390 at mailman.qth.net> wrote:

> To all doubters:
> my splitter/combiner ist a standard circuit, many solutionss can be found
> on the web. From .3 to 30 MHz both output ports exhibit the same signal
> amplitude when each port is terminated with 50 Ohms. The difference in
> receiving performance is definitely that my R-390A is inferior to my 51S-1
> which it should not be. I use the symmetric antenna input of the R-390A
> with a balun that transforms 120 Ohms symmetric to 50 Ohms unsymmetric.
> -Karsten-
>
>