[GreenKeys] Autostart freq for 170 shift RTTY

Fri Jan 1 17:49:49 EST 2021

I forgot to mention that Lissajous patterns could easily be used to 
check these different frequencies from one reference (e. g. 425).  All 
these numbers being related to each other by a integer factor.

Back then access to an accurate counter was rare. So one had to use 
trick to set frequency.  Scopes weren't cheap back then either, but you 
didn't need a fancy one to do the Lissajous patterns.

This chart might be of interest.

1 	85 		
2 	170 	Narrow shift 	
3 	255 		
4 	340 		
5 	425 	some commerical shift 	tuning fork
6 	510 		
7 	595 		
8 	680 		
9 	765 		
10 	850 	wide shift 	
11 	935 		
12 	1020 		
13 	1105 		
14 	1190 		
15 	1275 	Eu mark 	
16 	1360 		
17 	1445 	Eu space 	
18 	1530 		
19 	1615 		
20 	1700 		
21 	1785 		
22 	1870 		
23 	1955 		
24 	2040 		
25 	2125 	NA afsk mark 	5x425
26 	2210 		
27 	2295 	NA afsk space 170 shift 	
28 	2380 		
29 	2465 		
30 	2550 		
31 	2635 		
32 	2720 		
33 	2805 		
34 	2890 		
35 	2975 	NA afsk space 850 shift 	7x425
36 	3060 		
37 	3145 		
38 	3230 		
39 	3315 		

John, W9DDD

On 12/30/2020 5:25 PM, Ralph Mowery wrote:
> Just to add a few items to this.
>
> Rtty was allowed on the ham HF bands, but it was just a make and break
> similar to CW and not the  two tones that have been used for many years.  I
> think the audio two tones on AM was  legal on the old 11 meter frequency
> before the hams lost it to the CB.
> The VHF bands could use the audio so much of it was on AM and used the two
> tones mentioned for that reason.
>
> As many of the receivers and transmitters were not all that stable years ago
> the FCC let hams use any shift up to 1000 Hz (cycles back then) so they
> stayed at 850 shift for many years .  As the gear became more stable the 170
> hz was used as it was 850 divided by 5.  Not sure why they used 5.
>
> ON HF any tone pair could be used as long as it was 850 or 170 hz
> separation.   When ssb became more common and it was found that clean audio
> put into the microphone input would generate signals like the two tone shift
> and was legal.  I really hate it when people say AFSK on the low bands by
> putting RTTY into the mic jack of a SSB transmitter as the result is not
> really AFSK like it would be if AM or FM was used.  So the same gear could
> be used on HF or VHF (which was usually AM or FM) the tones of 2125 and 170
> or 850 up were used.  To generate clean tones out of the SSB transmitter it
> is advised to stay above 1500 Hz for the mark so the 2nd and above harmonics
> will be past the 2.2 or 2.5 khz ssb filter in many rigs.
>
> Ralph ku4pt
>
>
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net
> [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of w9ddd at tapr.org
> Sent: Wednesday, December 30, 2020 5:41 PM
> To: harold at w6iwi.org
> Cc: greenkeys at mailman.qth.net
> Subject: Re: [GreenKeys] Autostart freq for 170 shift RTTY
>
> Hi all,
>
> I'll make some comments that aren't necessarily facts, bit tidbits that may
> help trigger some one else's memory.
> First amateur RTTY was only allowed on VHF and higher frequencies. Why 2125
> and 2975.  The 850 shift was in use on commercial circuits. Some commercial
> used 425 shift. 2125 is fifth harmonic of 425. 2975 is seventh harmonic of
> 425.  You can crate a frequency standard with a tuning fork (I made one).
> Mark was probably low because a closed keyboard contact switches in more
> capacitance, therefore lower frequency.  Not sure why space is low on HF.
> Also inherited from commercial use?  Not much SSB in use at the time hams
> were granted HF RTTY! Even less folks would have thought of using the SSB
> mode of a transmitter to do RTTY in that era.
>
> I'm still trying to remember how I did 14,070 auto start with a KWM-1 around
> '71.  I remember I was shifting the PTO by making an adapter that plugged
> the PTO tube socket, running in CW mode and dropping the drive level to keep
> from overheating the finals.
>
> John, W9DDD
>
>
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