[Hallicrafters] Short metal tube mystery

[Carl]

The 717A was a favorite swap back in those days. It was basically similar to 
a 6AK5 mounted horizontal and developed as a replacement for 45-60 mc radar 
IF strips using noiser tubes. It was also a sharp cutoff which messed up ths 
AVC.  We called them mushroom tubes, they had a pin 1 grounded metal shell 
like regular metal tubes.

I had them in the RF and first IF in a HQ-129X where it made a huge 
improvement in 10-15M sensitivity but there was lots of overload on 40-80 
and I had to keep going back to the 6SS7 in the RF when changing bands.

These days they are an audiophool favorite and hams have discovered that the 
6SG7 and 6SB7Y make better front end subs in many sets.

Carl
KM1H



----- Original Message ----- 
From: <mikeqrpfun at aol.com>
To: <hallicrafters at mailman.qth.net>
Sent: Wednesday, October 27, 2010 9:54 PM
Subject: [Hallicrafters] Short metal tube mystery


>
>
> Hi folks,
> My long time ham buddy (W6LPU) and I have been recently sharing SX-28 
> stories and would appreciate some insight from you experts. I recall as a 
> teenager that my SX-28 housed small non-OEM metal tubes in the center 
> shielded RF section. I recall they were electrically equivalent 
> replacements to the ubiquitous 8 pin OEM octal 3" tall metal tubes (like 
> the ones in my BC-348-Q) but these puppies were only about an inch tall 
> with a slight dome on top.
>
> They supposedly offered better performance than their taller brethren. My 
> buddy isn't resonating with my recollection thinking instead I was 
> recalling "loctals" that have a very short distance between the pins and 
> the elements so that they could be used in the VHF spectrum. He said his 
> SX42 uses them saying they were pretty much duplicates electric-wise of 
> the 6SXX series except they were labeled 7XXX.
>
> Seems this same good old buddy gave me one of his SX-28A receivers a year 
> ago that I am getting ready to restore and would greatly appreciate you 
> fine folks clearing my"brain fog" and forward your recollections of this 
> mystery tube series and perhaps some part numbers that I so vividly 
> recall.
>
> 73 and thanks in advance,
>
> Mike
> WB6UTW
>
>
>
>
>
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