EF93, ECH81 Valves

[pwdrive]

Has anyone constructed an RF amp using the EF93 (6BA60) ?

Does anyone know if an ECH81 is any good at 30 Mhz, both as mixer and osc?

Lawrence.

[Steve_P]

Well it will but it'll have to be a new valve as this end of the spectrum will fall off first.

The EF93 will work as an RF amp at the lower frequencies.

Cheers,

Steve P.

[pwdrive]

Hi Steve, the ECH81 will be a new one, since my original post I have found out that at least one comms. receiver used the ECH81 up to 30 Mhz.

The EF93 is good to 30 Mhz but I was wondering if anyone had any practical homebrewing experience with this valve as an RF amp.

Lawrence..

[Skywave]

Many moons ago, I did do a 're-valve' job on an HRO using 2 6BA6 as the R.F. amps.: no problems, as I recall.

The 6BA6 and the ECH81 are a common choice for several Eddystone receivers: the S.888 / S.888A and the S.750 being two that spring to mind.

Having said that, for a mixer, I would use a 6U8 / ECF82 with cathode-coupled osc. injection: substantially lower e.n.r. as a mixer; excellent osc. / mixer isolation. Shouldn't present any serious problems @ 30 MHz; probably O.K. to 50 MHz.

HTH,
Al.

[pwdrive]

Many moons ago, I did do a 're-valve' job on an HRO using 2 6BA6 as the R.F. amps.: no problems, as I recall.

The 6BA6 and the ECH81 are a common choice for several Eddystone receivers: the S.888 / S.888A and the S.750 being two that spring to mind.

Having said that, for a mixer, I would use a 6U8 / ECF82 with cathode-coupled osc. injection: substantially lower e.n.r. as a mixer; excellent osc. / mixer isolation. Shouldn't present any serious problems @ 30 MHz; probably O.K. to 50 MHz.

HTH,
Al.

Thanks Al, it's for that Regenerodyne heap I hope to be working on again, I have decided to go minature glass instead of octal for the receiver, for the osc/mixer I will try both the ECH81 and a ECF82 and see what's what, I am wondering what advantage there would be by going the cascode RF amp route so far as antenna to mixer isolation goes or any other possible advantages, just to re cap the reciever will tune from 1.6 Mhz to 30 Mhz, any thoughts?

Lawrence.

[Skywave]

It's good that you have returned to your project: we discussed so much about it and in great depth quite some time ago. During those sessions, I do recall this topic of pentode vs. cascode arising. Can't recall, off-hand, what I said at the time: however, I expect that what I did write is still available in those old posts.

Al.

[pwdrive]

It's good that you have returned to your project: we discussed so much about it and in great depth quite some time ago. During those sessions, I do recall this topic of pentode vs. cascode arising. Can't recall, off-hand, what I said at the time: however, I expect that what I did write is still available in those old posts.

Al.

I think I posted too much in the original Regenerodyne thread, I think I need to condense my notes...

Lawrence.