[Hammarlund] SP-600 JLX-15 vlf rcvr - NOT!

[Kenneth G. Gordon]

> Hi Ken,
> Is AL correct with the JLX-31 being xtal controlled on the vlf band?
> My quest goes on for a RBL-3 competitor. bob...w2ami

First of all, we must get this completely clear. The subject receiver, the 
SP-600-JLX-15 is NOT, repeat NOT, a "vlf receiver", period. It covers 
SOME OF the 30 through 300 Khz LF band, but not all of it. It covers 
NO VLF frequencies at all.

Secondly, in the answer to your question as to whether or not the  JLX-
31 is crystal-controlled on "the vlf band".  It may be. I've never had one. 
The letter "X" in the nomenclature would certainly indicate that the JLX-
31 has PROVISION for some crystal controlled channels, and the "L" 
would indicate to me that it has some LF capability. But what that is, I 
do not know.

However, when you say "in the vlf band" you had better make perfectly 
clear what you mean by that. In point of fact VLF means ONLY 
frequencies from about 10 to about 30 Khz, the bands between 30 and 
300 Khz are LF, the bands between 300 Khz and 3.0 Mhz are 
considered MF, and 3 to 30 Mhz is called HF.

There is no single "vlf band" that covers from 10 Khz through something 
more than 30 Khz.

Now, I repeat, and this is a very important distinction:

The SP-600-JLX-31 is NOT, repeat NOT, 
the same receiver as the SP-600-VLF-31 !!!!!!!!!!!

Not by a long shot!

As I understand it, the SP-600-JLX-31 is simply one in a long line of HF 
band, or combined some-bit-of LF and HF band receivers.

The SP-600-VLF-31 is a COMPLETELY different design, having 
different IF frequencies, and totally different main frequency coverage.

The SP-600-VLF-31 continuously covers 10 Khz through 1500 Khz in 
seven bands.

The ONLY thing they have in common in the nomenclature is the 
number "31" at the end. They are COMPLETELY DIFFERENT 
RECEIVERS, period.

There are several receivers that would be a significant upgrade to your 
RBL-3 (of which I have several, BTW). They are the SP-600-VLF-31, 
the RCA SRR-11, the National AN/WRR-3, the Collins R-389, and 
several others more difficult to find.

As of now, I have several each of the RAK, RBL, SRR-11, and one R-
389. I had to sell all three of my SP-600-VLF-31s, so I have no more of 
those, and I have never had an AN/WRR-3, although there is one for 
sale now on the Milsurplus list.

We absolutely MUST get the distinction between the SP-600-JLX-31, or 
-15, and the SP-600-VLF-31 clear before we can do any more 
discussion on their relative merits. They are NOT the same receiver!

Ken Gordon W7EKB