[HBR] New member from Brazil

[Carlos Alberto - PY4QE]

Grateful for the good ideas people.

In fact the 2x4 +1 was the first project that I saw and has served as
inspiration.

>Walt said:
> A few things occur to me.
>
> 1. Vacuum tube auto radios were often built with 262 kcs IFs, thus
> junker auto sets from the 1950's-60's might be a source.
I saw this idea in the old posts and tried to find something here, but so
far nothing.

 2. Ham band only tuning (but not band imaging) is obtainable with the
> main tuning cap from an FM receiver, in the U.S., 88-108 Mcs.  Again,
> a junk set might provide what you need and (possibly) a dial mechanism
> that could be adapted.

I'm trying with colleagues from other cities, mainly in Sao Paulo.
Let's see what comes up. Here also the FM band is 88 to 108.

> 3. If you do 80-40M band imaging with an IF of 5500 kcs (or so) -- this
> requires a crystal filter of some sort, OR double conversion (...)

1700 kc was chose only because I have two crystals at this frequency. In
fact, I also saw a interesting receiver with 7 tubes, toroids in the
preselector and VFO, and a 7360 in the first mixer (George Dittmar - W0HIO).
Double conversion 1700 kc with crystal filter and two 455 kc IFT.
The idea of a low freq. 1st oscillator in the 1500-2000 kc range is very
good for the stability view.

> I have a set with this design which uses a push-pull oscillator
> driving a push pull mixer (both dual triodes) to give single-end IF
> output.

Are these common triodes like 12AT7 or 6J6s?

> This design does have a spurious response where the third harmonic of
> the oscillator passes through the 5500 kcs IF.

To avoid this, I think a 2nd LO xtal at 2155 kc is better than the 1245 kc
VFO from the original circuit.
It uses a VFO there for some sort of fine tune SSB clarifier. Since I'm
thinking in a xtal oscilattor, this clarifier will be in the main 5200~5700
kc VFO, because the BFO will be also a xtal at 453,5 kc.

> You could use a 2nd IF of 262 kcs using three auto radio IFTs and get
> tolerable performance -- perfectly adequate for AM, or (with audio
> filter) CW.  This would require one IF stage at 5500 with fairly high Q
> coils to control images.

If I get the 262 kc IFT, this is a good approach. Quite easy because custom
crystals here are cheap.

> I agree with Ian that the Super SimpleX and 2X4+1 designs are a useful
> starting point.

I also think, this was my first idea and within the philosophy of keeping
things simple, I think that is the way to go until I get more time and
skills.
And then I can try more complex projects. Let's see.

I thank all the ideas and suggestions and will keep you posted.

73, Carlos PY4QE


----- Original Message ----- 
From: "Walt Hutchens" <waltah at earthlink.net>
To: "HBR Receiver List" <hbr at mailman.qth.net>
Sent: Monday, August 31, 2009 6:37 PM
Subject: Re: [HBR] New member from Brazil


> Carlos said:
>> Like I said, the biggest problem here is to find all the parts, mainly a
>> adequate variable capacitor, trimmers and the dial.
>
> A few things occur to me.
--------snip---------- 

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