[ARC5] RBA-1 - Field Change #3.

[Mike Feher]

Yes, a mere "500 kHz" as you put it is a large change. However, 500 Hz is
not, and, it is on the low band of the receiver's band selection. Even
percentage of BW wise it is a nit. I have not looked at my RBA downstairs,
but, I would not be surprised that it would already tune down 500 Hz below
the 15 kHz bottom limit as it is, without CN-3. Remember, data rates at
those frequencies were pretty slow due to the high Q at the transmitters, so
modulation bandwidth did not take up much space. I really doubt that they
were using 30 WPM down at 15 KHz. Just the rise and fall times of OOK at
that rate would not be passed down there and all the characters would just
blend together as they would be essentially integrated. 73 - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 


-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Kenneth G.
Gordon
Sent: Wednesday, June 17, 2015 12:18 PM
To: ARC5
Subject: Re: [ARC5] RBA-1 - Field Change #3.

On 16 Jun 2015 at 23:56, Roy Morgan wrote:

> On Jun 16, 2015, at 9:18 PM, Mike Feher <n4fs at eozinc.com> wrote: 
> > Wow - wonder what the incentive was to lower the receiver range by a 
> > mere 500 Hz? 73 - Mike

Well, for one thing, at VLF "...a mere 500 kHz..." was a relatively large
"distance".

> Cutler, Maine operated (and may still operate) on 17.8 kc.

Yes.

> Station NSS in Annapolis operated on 21.4 kc as I understand it, but 
> other Navy VLF stations may well have operated just below 15 kc.

Back in the 1970s, when there were a lot more Navy stations on VLF, I was
working for a fellow who was using those stations for VLF propagation
research. None were below 16 kHz, as I remember it.

There was one in Panama, and another in North West Cape, Australia. 

NWC in Australia was copyable in Missoula, Montana 24/7/365. Although the
signal level would drop pretty low during the day, it was always there.

There was another in Jim Creek, Washington. The signal level in Missoula,
Montana was strong enough to copy with a short, wet string for an antenna,
and a razor-blade for detector 24/7/365.

The antenna was pretty impressive, being strung between two parallel
mountain ranges.

I used the Navy stations for code-practice at the time, since they were
still all on CW at about 30 WPM, 5 letter code groups. I used a brand-new
RAK for the inhaling duties.

Great fun, and darned good practice too.

Ken W7EKB
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