[HBR] Re: W0VLZ's Simple-X receiver

[Niel Wiegand]

Kees,

My regen-superX receiver at 
http://www.io.com/~nielw/3tube_xtal/3tube_xtal.htm evolved from the two 
tube superhet shown in the early 40s handbooks. This design used 1/2 of 
a 6C8 dual triode as a regen detector. When I first built this 1940s 
design I didn't like the stability and overload handling of the triode 
regen IF detector. I immediately added a BFO. One mod lead to another 
and I ended up with a 6J7 regen detector with feedback in the plate circuit.

It was an easy mod to replace the 6J7 grid coupling cap with a crystal.
This simple crystal filter does not include the usual phasing and 
selectivity adjustments.  Max selectivity occurs just before the 
detector breaks into oscillation and the peak is at the xtal freq. By 
varying the BFO freq wrt the xtal frequency I change the pitch of signal 
at the peak.

I can use the regen action of the detector to copy CW but I lose control 
over the crystal filter characteristics. Having the BFO let me vary the 
amount of selectivity (by varying the amount of regeneration without the 
detector being in oscillation) and apparent peak frequency (by varying 
the BFO frequency).

73,
Niel


> Date: Wed, 31 May 2006 21:48:53 -0500
> From: windy10605 at juno.com
> Subject: [HBR] Fw: Re: Simple-X receiver
> To: hbr at mailman.qth.net
> Message-ID: <20060531.214943.2608.0.windy10605 at juno.com>
> Content-Type: text/plain; charset=us-ascii
> 
> Now we're cookin'. That's exactly the rationalle I came up with to use a
> regen stage to make up for crystal filter losses ....figured they would
> offset very nicely. Thanks for sending the links Niel. I have access to a
> qty of 1612Khz crystals so that only cuts off the very top end of 40m.
> 
> Question; Can't you use the regen control for a BFO function ?
> 
> 73 Kees K5BCQ
> 
>    
>  > --------- Forwarded message ----------
>> From: Niel Wiegand <nielwiegand at aggienetwork.com>
>> To: hbr at mailman.qth.net
>> Cc: windy10605 at juno.com
>> Date: Wed, 31 May 2006 20:53:25 -0500
>> Subject: Re: Simple-X receiver
>> Message-ID: <447E4895.6070000 at aggienetwork.com>
>> References: <20060601001039.75BAE859C29 at mailman.qth.net>
>> 
>> I've had pretty good results with a 80/40 mtr superhet running with a 
>> 1700KHz IF. See http://www.io.com/~nielw/3tubrcvr/3tubrcvr.htm and 
>> http://www.io.com/~nielw/3tube_xtal/3tube_xtal.htm This project started 
>> out as the two tube superhet shown in  February 1941 issue of QST but I 
>> changed the detector to a 6J7 and added a BFO. I also put a crystal in 
>> the middle on the regen feedback loop, helping selectivity a lot.
>> 
>> It is drifty for the first few minutes but once stabilized it is fine. 
>> Since the same HFO freq range/HFO coil for both 80 and 40, there no need 
>> to restabilize after changing bands.
>> 
>> My external antenna tuner provides additional image frequency rejection. 
>> I've not noticed an image problem.
>> 
>> This rcvr is a good match for my 6J5/6L6 xmtr. See 
>> http://www.io.com/~nielw/2tube_xmtr/2tube_xmtr.htm
>> 
>> Niel - W0VLZ
>>