[ARC5] What the heck is a "1/2 harmonic Q-5er?

[Kenneth G. Gordon]

On 11 May 2020 at 8:30, Bob Groh wrote:

> The mixing takes place in the BC-453 - the BC-348's IF signal is 
> loosely coupled to the mixer tube in the BC-453.  The BC-453 is then 
> tuned to 415 kHz - that means the 453's LO is 85 kHz higher or 500 
> kHz.  The 2nd harmonic of the 453's LO is at 1,000 kHz and that 2nd 
> harmonic mixes with the 915 kHz IF signal from the BC-348 and the 
> result is (Wala!!) 85 kHz. 
> 
> This can all be done in a non-destructive way to either radio.
> 
> The article that goes into wonderful detail on all of this in Electric 
> Radio Issue #304 September 2014 (pg 18 on) and authored by Joe 
> Long, WA2EJT.  I have had a chance to look at the article (pdf copies 
> are NOT legitimately available!!!) and I am going to buy a copy of that 
> issue for my own use (as soon as I decide what else I want to get to 
> make the minimum $10 order threshold - shipping is free, by the 
> way).  It is a wonderful article with tons of great information including 
> selectivity curves, information on using the same idea with other 
> radios, etc. As a long-time ham and a retired electronics engineer 
> with a long history in designing RF radios, I whole heartedly 
> recommend getting your own back issue!  After I've gotten mine of 
> course. 

Well, quite obviously, I was wrong about the process. I dug out my copy of ER and re-read 
the article. Joe's explanation of the process is somewhat confusing to me, and Bob's 
explanation is far easier to understand....and more succinct. Thank you, Bob.

But see below on another issue.

>     The original article about the 455 KHZ Q-5er use of the BC-453 said that it did not matter if 
>     you used the BFO of the receiver or the BFO of the BC-453, so I guess an R-11A/R-511 
>     would work as well, in addition to taking advantage of the superor construction of the Type 
>     12 set.

Well, yes, and no. As you obviously know, the Type 12 gear does not include a BFO, so you 
would have to use the BFO in the BC-348.

Or, if your R-11 is like mine, hacked to ribbons already, you could remove the noise-limter 
stage and install a BFO transformer from a junked BC-453 or R-23. 

I would prefer to have the BFO as near to the final detector stage as possible so that it won't 
interfere as badly with whatever AGC is in the R-11.

Ken W7EKB