[Premium-Rx] Fw: Noise Power Ratio Testing of Radio Receivers

[Peter Rovardi]

----- Original Message ----- 
From: "Peter Rovardi" <peter.rovardi at btinternet.com>
To: "PREMIUM-RX" <premium-rx at mailman.qth.net>
Sent: Wednesday, December 05, 2012 11:23 PM
Subject: Re: [Premium-Rx] Noise Power Ratio Testing of Radio Receivers


> Hello,
>
>
> This dicussion about NPR and IMD brings back  memories of attempts (albeit 
> more a learning curve, circa 1987) for improvment of  IMD on my Drake TR7 
> PA  along with general "front end" receiver improvements / experiments.
>
> As I recall, I fitted an  extra pair of 48.05Mhz Drake roofing filters (8 
> poles total), in series with the original filters on the up-convertor 
> board. The board is common for both TX and RX sigs.     I found by using 
> wideband audio "pink noise" feed at the mic. input  gave by far the best 
> results  for observation  of  the "actual" TX filter bandwidth on the 
> spectrum analyser, and was also a very usefull tool for observing exactly 
> what happens on PA overdrive ect, as this signal "fills in" so to speak, 
> the full filter passband, mixer spuri  warts and all!  A sort of  NPR in 
> reverse, I suppose?
>
>
>
> 73,s
> Peter G4HSB.
>
>
>
>
>
> ----- Original Message ----- 
> From: "Michael O'Beirne" <michaelob666 at ntlworld.com>
> To: "PREMIUM-RX" <premium-rx at mailman.qth.net>
> Sent: Wednesday, December 05, 2012 9:23 PM
> Subject: Re: [Premium-Rx] Noise Power Ratio Testing of Radio Receivers
>
>
>>
>> Gents
>>
>> The comment attributed to Ulrich Rohde was in voiced some years before in
>> one of Pat Hawker's Technical Topics pieces. I can't place in which 
>> issue.
>>
>> I well recall at the time thinking along parallel lines in relation to 
>> the
>> then eagerness  to achieve the maximum carrier suppression for SSB but
>> ignoring (or forgetting) that the transmitter's IP3  products were at 
>> vastly
>> higher levels and would completely mask any residual carrier.
>>
>> As for PAs, I still stand by traditional valved ones.  Angus McKenzie's
>> spectrum shots in his review of the Trio TS83S in the old "Amateur Radio"
>> are absolutely stunning, the level falling by 75dB within about +/- 3.5 
>> kHz.
>> It used a pair of 6146 valves.
>>
>> 73s
>> Michael
>> G8MOB
>>
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>