[Milsurplus] RBC - mods

[Kenneth G. Gordon]

On 16 Jun 2016 at 12:31, George Babits wrote:

> Ken,
> 
> I wonder what percentage of cobbled up product detectors were really an 
> improvement?

Not only PDs, George: IMHO, most "modifications" to any of our gear.

>  Maybe 10%?

That much? I think much fewer.

>  I have had SX-28, R-388, R-390, Super Pros, and 
> SP-600 receivers with prodector modifications.  All were pretty dismal. 
> Tells me that the average modifier really didn't know what he was doing.

I have never, ever said any such thing.

I will repeat what I have said many times: the original designers of MOST of our old gear 
were no dummies. They were highly intelligent and capable men. Some, in my opinion, were 
sheer geniuses. Like Dr. Drake and his boys at ARC, for instance.

Even so, we HAVE learned a few things since then which CAN improve those rigs. AGCs 
and detectors. Noise limiters too, perhaps.

But, any mods have to be properly designed and implemented for the particular rig, and 
everything about the old rigs has to be taken into account before the soldering iron is even 
plugged in. Some of us are STILL learning about some of the very interesting features 
designed into the "ARC-5" receivers, for instance. WHY the designers did what they did is 
very important to know or to figure out before someone even THINKS about "modifications".

I would venture to say that well over 90% of the usual "ham" modifications to our old gear 
makes them work WORSE than they would if left alone.

My thoughts on "modifications" pretty much follows the medical doctor's rule, "First, do no 
harm." Most mods do lots of harm, mainly to those features of a rig that the "mod designer" 
never even considered.

In my almost 60 years as a ham, I can remember, at most, two modifications which actually 
helped the associated gear, and I can't even remember now what those were.

Even so, my PD mod to my BC-779 made an immense improvement to it. Perhaps I was 
lucky, or perhaps the original problems with it could have been handled a different way.

There were two very annoying problems with my first, almost new, BC-779: 1) the BFO 
injection level was way, way too low. A strong CW signal would simply overwhelm it. I had to 
ride the RF gain control constantly. And 2) it was extremely noisy. I mean internally 
generated noise from the mixer stage and other stages was way too evident. It masked 
weak signals. There was a constant, loud hiss from it.

My PD mod fixed both problems, making that BC-779 a real joy to use. 

I especially liked the '779's variable IF band-width feature, and the wonderful crystal filter. 
Hammarlund's crystal filter design was WAY ahead of everyone else's at the time. After my 
experiences with that receiver, my respect for Hammarlund went way up.

Ken W7EKB