[Elecraft] K3, VHF Diversity

[David Anderson]

Hi Harry,

You are correct on satellite operation a full duplex rig is useful so you can net your signal on the other station as there you are for example transmitting up to space on 70cm and receiving the transponded signal on 2m. On high orbit satellites the slight delay is off putting if you listen to your own voice delayed and you can tend to stammer!

However Chuck is writing about 144MHz moonbounce not OSCAR satellite operation. 

O moonbounce via "OSCAR 0" we can listen to our own signal, but don't need a full duplex rig to do that because of the 2.5 second delay of our own moon echo. Typically you hear a lot of echo testing which goes like this on CW at 15wpm: Transmit "OOOOO" with a huge ERP then back to receive a weak and watery "ooooo" if you are lucky and the gods are willing. 

Sometimes the shift in polarisation through the ionosphere (Faraday rotation) causes the signal to come back at 90 degrees to what you sent it up at and then you will generally hear nothing. This is where having dual receivers, one on Horizontal polarisation and the other on Vertical polarisation would help a lot. 

On 23cm and higher frequencies, moonbounce is generally transmitted on circular polarisation and even this requires a bit of thought because the mirror reflection off the moon converts right hand circular into left hand circular, so your antenna feed system to your dish has to cope with that.


73

David Anderson GM4JJJ 

> On 19 Feb 2015, at 07:32, Harry Yingst via Elecraft <elecraft at mailman.qth.net> wrote:
> 
> Yes I understand the K3 is a Non-Duplex radio.
> Truthfully I have yet to really look at Sat Seriously and the last I really read up on it wasyears ago  (up on one band down on another) So for some reason I had it stuck in my mindthat you had to listen to yourself (Duplex) Something I'll need to read up on again.
> Thank you
> 
> 
> 
> 
>      From: Edward R Cole <kl7uw at acsalaska.net>
> To: Elecraft at mailman.qth.net 
> Sent: Thursday, February 19, 2015 12:19 AM
> Subject: Re: [Elecraft] K3, VHF Diversity
> 
> I guess I missed Chuck's posting on Feb.18th.
> 
> Harry:
> 
> First your question the K3 is unable to operate in duplex as common 
> ckts are used in the DSP (2nd IF) for both Tx and Rx.  Only simplex 
> operation is allowed.
> 
> 
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