[Collins] Collins 62S-1 Transverter Downconversion Gain??

[Pete]

Jerry,
The pertent 62S-1 manual info is:
	1. RX Signal path uses a 6ER5 Triode RF Amp followed by another 6ER5
triode as a Mixer.  
	2. Noise Figure approximately 4 dB
	3. System performance is such that: 1.2uV at 2M or 6M yields 10 dB
S+N/N on AM Signals through a 75S Receiver
(NOTE: the 75S3 receiver manual spec is 0.5uV yields 10 dB S+N/N) 

This information tells me the NF of the cascaded 62S-1/75S3 system is worse
than the noise figure of either the 62S-1 and the 75S. 
There has to be a net translation loss from VHF to HF in order to match this
specification.  I'm calculating there should be -8dB conversion loss based
on these specifications in the manuals.  Interestingly I'm measuring -12 dB
conversion loss.  But, I'd like some confirmation on what it should be. 
What do you think?
Pete
K5PZ

 

-----Original Message-----
From: Dr. Gerald N. Johnson [mailto:geraldj at weather.net] 
Sent: Saturday, September 18, 2010 10:32 PM
To: zilassoc at la.twcbc.com
Cc: collins at mailman.qth.net
Subject: Re: Collins 62S-1 Transverter Downconversion Gain??

Shouldn't need much gain, just enough so the 62S-1 RF stage noise sets the
NF of the system. A better check than gain is the NF of the system done with
a manual vacuum diode noise source and an AC VTVM on the IF audio output
with AVC turned off. To much gain introduces unneeded intermod from strong
signals. But since the 75S NF at 20 meters is probably 8 or 10 dB if the
system NF is going to get down to 2 dB for 2m and 5 dB for 6m, its going to
take maybe 15 to 20 dB gain in the 62S-1. 
There should be a detectable (not necessarily on the S-meter) noise rise in
the IF receiver when the 62S-1 is switched into the circuit. A few dB is
common, without checking system NF its hard to say how much there should be.
Some VHF operators would advocate a 10 dB rise and I think in most cases
that is way too much leading to intermod problems.

What does the 52S-1 use for RF stages in the receive side? I don't have a
manual on it.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 9/19/2010 12:02 AM, zilassoc at la.twcbc.com wrote:
> Does anyone know the 50MHz to 14MHz conversion gain or loss of a 
> properly operating 62S-1?  What about from 144MHz to 14MHz?  The 
> manual doesn't state this metric. Thanks for the bandwidth, 73 Pete, 
> K5PZ
>
>