[Elecraft] K3 if isolation of softrock lite used as panadapter

[Jack Smith]

Jerry:

You might first wish to measure the reverse isolation of a MMIC before 
you make that statement. While they are great devices, isolation is not 
their strong suit.

The Gali74, which I use for a variety of purposes, has an isolation of 
around 28 dB at the K2's IF frequency. The gain is 25 dB, so if you pad 
the output for unity  gain, you are around 53 dB. With a Softrock's 
typical -40 dBm LO leakage, that strikes me a bit on the marginal side. 



Jack K8ZOA



Jerry Flanders wrote:
> I assume a simple MMIC amp plus a simple resistive attenuator circuit 
> will provide enough isolation and also provide for matching levels 
> up/down as may be necessary. At least, that will be my first cut at 
> the problem unless somebody else comes up with a better plan before my 
> K3 arrives.
>
> At down east microwave ( 
> http://www.downeastmicrowave.com/cat-frame.htm ),
> see the 
> <http://literature.agilent.com/litweb/pdf/5967-6159E.pdf>INA10386 
> (DC-2GHz, 24dBG, 3.5dB NF +14dbm 1dB Gain compression ) for only $5. 
> Very easy to use something like this, I think.
>
> Depending on the signal level of the K3 IF output, we might get enough 
> isolation from  a resistive attenuator alone and still have a usable 
> signal level on the softrock panadaptor.
>
> I would much prefer a plug and play manufactured solution if it takes 
> more than an attenuator, but not an expensive one.
>
> Jerry W4UK
>
>
> At 07:29 PM 2/11/2008, stephen pearce wrote:
>> A month or so ago one of the Elecraft engineers pointed out that
>> if the softrock lite rx is connected directly to the if port on the k3
>> there was a significant issue with coupling of rf from the softrock
>> board into the
>> rx if of the k# with consequent degradation in rx performance ...
>>
>> Has anyone produced a design for a suitable isolation amplifier/
>> coupling stage which will
>> prevent this and still allow the softrock to be used (in conjunction
>> with a pc) as a panadapter?
>>
>> Thanks
>>
>>
>> -- 
>> Stephen Pearce
>> zl1any
>> Whangarei
>> _______________________________________________
>> Elecraft mailing list
>> Post to: Elecraft at mailman.qth.net
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>>  http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>
> _______________________________________________
> Elecraft mailing list
> Post to: Elecraft at mailman.qth.net
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft   
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>