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Date: Tue, 18 Dec 2012 18:49:42 +1100
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From: Dimitrios Tsifakis <dtsifakis@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: FT-241A xtals?
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Hi Paul-Henrik,

> Yes, the same thought has been on my mind for a long time now. The problem
> is that fundamental X-tals for this frequency band are nearly unobtainable.
> I have even tried to custom order some new ones for me and a couple of
> friends but never succeeded - the quantities would need to be much larger
> for this type of crystals. (They use a different kind of cut as compared to
> crystals for say 3500kHz which can still be ordered custom fairly easily)
>
> Hopefully people with a stash of suitable vintage X-tals will wake up when
> the new band opens for real and put some up for sale if they don't want to
> use them themselves.

I bought a few crystals from this ebay seller:

http://www.ebay.com.au/itm/FT-241-CRYSTALS-Many-to-choose-from-You-pick-/260897401407?pt=LH_DefaultDomain_0&hash=item3cbeb26a3f&_uhb=1#ht_4373wt_1188

There seem to be a few left. They are sold as-is, but I found that the
majority of the ones I bought worked OK. There may be other sellers on
eBay.

> I'd say go for it - I have built a couple of "MO-PA" transmitters for
> 80/160m, they are really pleasant and rewarding projects with a distinct
> sound of their own. This is especially true if you also key the oscillator.

I have built recently a similar transmitter for 40 m, using a 6CL6 and
an 807. When I keyed the oscillator together with the PA, I couldn't
get it to behave properly, so I added a switch to leave the oscillator
on and key only the cathode of the PA. I only key the oscillator when
I want to draw some attention with the home-brew sound!

In general, I have had difficulty sourcing a HV transformer suitable
for an 807. In the past, I found that one can build a voltage doubler
or quadrupler, with modern electrolytics, it is a viable alternative.
The 6.3 V for the filaments I found I can get from a 6 V transformer.
Hint: it's easy to add extra turns on a toroid type transformer :-)

73, Dimitris VK1SV