[HBR] Cost Of Homebrewing?

[hbr@mailman.qth.net]

In a message dated 10/9/03 9:00:17 PM Eastern Daylight Time, 
waltah@earthlink.net writes:


> Jim answered ... 
> > That's what the DCS-500 was.  
> 
> Thank you.  When I look at it with the proper squint, I can see that 
> the DCS-500 is indeed HBR knock-off -- basically, an HBR-11 done 
> with 10 tubes.   However the only improvements I can find are in the 
> IF section: 4.5 Mcs half-lattice crystal filters replacing the 1600 kcs 
> first IFTs and adjustable selectivity via coupling variation between 
> pairs of 50 kcs IFTs.   

Agreed! 

They did provide a transistorized 100 kcs 
> 
> calibrator in place of the 3.5 Mcs marker.  And the RF stage is a 
> 6BA6 -- a better choice than the (sharp cutoff) pentode section of a 
> 6AZ8 as used in the HBR-11.


But didn't the DCS-500 come first, except for the HBR-14? 

> 
> They deleted the 6BY6 product detector of the HBR-11 in favor of a 
> diode -- a definite step backward -- and replaced the 6BJ6 IFs with 
> 6BA6's.  Otherwise the tubes are pretty much the same types as the 
> HBR-11. 
> 
> The 2nd detector isn't the only weakness.  The BFO is coupled 
> directly from the oscillator cathode -- unless you keep the signals 
> very small at the 2nd detector, you're going to have distortion caused 
> by BFO pulling.
> 
> They used a truly crummy tuning cap -- a National HFD-30-X.  Boy 
> the thing must have been a joy to tune.   There's not that much 
> backlash in the sleeve bearings -- the rear is a friction finger type -- 
> but the torque is pretty high.   And pinch/planetary dials don't 'do' 
> torque.   
> 
> The 1st oscillator is the triode half of the 6U8 1st mixer, with no 
> buffer.   Only the HBR-11 had that configuration -- the others of the 
> series used a 6BH6 ECO.
> 
> And they kept the worst feature of the HBR-series.  Having worked 
> for a few weeks with a receiver with a tuning rate of  28 kcs/knob 
> revolution (the 1MHBR) I have a very hard time picturing the use of a 
> National ACN/ICN/SCN dial -- 2.5 revolutions to cover 500 kcs = 200 
> kcs/revolution ... is it even *possible* to tune in an SSB signal on 
> such a receiver?   That's double the tuning rate of a 3-6 Mcs 
> command receiver, for goshsakes.  The only thing that can be said 
> for those dials is that compared to other new-purchase dials they 
> were pretty cheap in 1960. 
> 
> "Improved in the ARRL lab and published in the handbook"?   Only 
> the latter, I'm afraid.   Overall, the DCS-500 isn't as good a design as 
> the HBR-series.

Agreed, particularly the dial. But the dial/capacitor thing was easily fixed. 
Same for the rx "rear end". 

My point was not that the DCS-500 was a great rx but that it was the last 
tube rx to come out of ARRL Hq that could really be called "general purpose" or 
"mainstream" - meaning it had all bands and selectivity for all popular modes. 
After the DCS-500, the rxs all have multiple compromises that are difficult to 
get around, such as SSB-only selectivity. Indeed, after the DCS-500, the 
semi-serious CW (or AM!) op was completely ignored in the rx department. 

Perhaps the explanation is that after the DCS-500 knockoff, a series of non 
Hq. HBR-type articles followed for several more years. Not just the W6TC 
articles but others like W2PPL's "HBR-453", based on the Q5er Command set, and 
W1ICP's BC-454/converter setup for beginners. 

73 de Jim, N2EY


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