[ARC5] 10-Meter 274N RX - The 20-27 RAT-1

[Mike Everette]

The 717A, I am pretty sure, is "an octal based 6AK5."

It's a good tube; but the 6AB7 might actually be a better choice.  Without looking up tube characteristics, I am also pretty sure that the 6AK5 is a sharp-cutoff-type which doesn't respond to AVC action as well as a remote-cutoff would.  The 717A is, I think, also sharp-cutoff.  The 6AB7 is remote-cutoff.

Now, I'm not saying that progress is unnecessary; far from it.... but note:

For those who are of the opinion that older, longer-lead tubes are inferior, consider receivers like the National HRO (original) with its 6C6 and 6D6 tubes, which remains one of the quietest and most sensitive of tube receivers.  Perhaps an even better example is the RCA AR-88, which is so hot even with old octal types that it can, and will, hear the world WELL with only a few feet of antenna.... even on ten meters.

Been there, done that, and have shirts with both National and RCA logos to prove it.  And my receivers are un-hacked; they run full-stock.  

Many receivers died horrible deaths back in the day on account of ill-advised "hacking" on the part of hams who followed the advice of ill-conceived articles in magazines like SeekU.... ripping out not only the first RF stage, but entire front ends in a quest for that extra tenth-of-a-microvolt, often resulting in a howling, squalling tangle of untameable feedback that caused the whole project to be shoved off the bench and kicked under the table -- or chucked into the dempsty-dumpsty.

73

Mike
W4DSE


--- On Sat, 2/9/13, john rose <brokenthumb at live.com> wrote:

> From: john rose <brokenthumb at live.com>
> Subject: Re: [ARC5] 10-Meter 274N RX - The 20-27 RAT-1
> To: "arc5 mail list" <arc5 at mailman.qth.net>
> Date: Saturday, February 9, 2013, 2:28 AM
> 
> Fair Radio. Part# 717A-UN  $15.00 each
> 
> ----------------------------------------
> > From: kgordon2006 at frontier.com
> > To: arc5 at mailman.qth.net
> > Date: Fri, 8 Feb 2013 21:08:38 -0800
> > Subject: Re: [ARC5] 10-Meter 274N RX - The 20-27 RAT-1
> >
> > On 8 Feb 2013 at 21:42, Geoff wrote:
> >
> > > For G&G try a 6AB7 and 6AC7 if you can work
> out a quick way to solve
> > > the filament issue and compare to the mushroom.
> > >
> > > Carl
> >
> > Actually, the 'shroom' is a pretty good tube....ifn you
> can find one for a
> > reasonable sum now.
> >
> > I have looked for 717As on eBay and have had
> difficulty.
> >
> > Ken W7EKB
> >
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