Re: LF: Better picture of the 807 based 500kHz TX

[M0FMT <m0fmt@yahoo.co.uk>]

OK Mal

 

Point taken. I was referring to a "Power" oscillator like a single 6L6 used as an Xtal oscillator running at 15 / 20Watts which means normally there is insufficient current (really) from a VR tube for the Anode(plate) so all that is necessary is to stab the screen. Otherwise I totally agree.

I do know the standard T1154 chirps well. There is a PA0 who runs one on 500 and I am sure you have worked him it is like a signature signal HI. 

I think there was some kind unpleasantness going on at the time of the T1154 manufacture so the fine points of frequency control was probably a low priority.

73 es GL Pete M0FMT IO91UX

From: mal hamilton <g3kevmal@talktalk.net>
To: rsgb_lf_group@blacksheep.org
Sent: Wednesday, 19 December 2012, 11:55
Subject: Re: LF: Better picture of the 807 based 500kHz TX

Hi Pete

Stabilise both Plate es Screen on an Oscillator, followed by a Cathode follower to avoid chirp and osc pulling.

The T1154 was very unstable with a bad chirp, surprised it ever passed Quality Control

G3KEV

 

----- Original Message -----

From: M0FMT

To: rsgb_lf_group@blacksheep.org

Sent: Wednesday, December 19, 2012 10:08 AM

Subject: Fw: LF: Better picture of the 807 based 500kHz TX

 Try again minus cct too big I think.

73 es GL Pete M0FMT IO91UX

----- Forwarded Message -----
From: M0FMT <m0fmt@yahoo.co.uk>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, 19 December 2012, 9:52
Subject: Re: LF: Better picture of the 807 based 500kHz TX

Hi Dimitris and group

 

I have not seen the schematic but it is usual to stabilise the screen of a power oscillator to reduce chirp on key down.

Now you have shown us yours I will show you mine. I usually sketch the schamatic after the event so foregive the presentation on the back of an envelope.

I now get at least 4Watts after adjusting the ant link coupling away from the chasis. Best audible DX Kent 80miles best Opera DX PA0 land.

73 es GL Pete M0FMT IO91UX

From: Dimitrios Tsifakis <dtsifakis@gmail.com>
To: rsgb_lf_group@blacksheep.org
Sent: Tuesday, 18 December 2012, 23:46
Subject: Re: LF: Better picture of the 807 based 500kHz TX

2012/12/19 Graham <g8fzk@g8fzk.fsnet.co.uk>:
> Why the  stabilised  screen  supply ?
> G..

It's embarassing. I like the glow of VR tubes! :-)

73, Dimitris VK1SV