[TenTec] cw creation

Tue Apr 26 20:10:57 EDT 2005

Continuous Wave.

Tommy

W4BQF

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Steve Baron - KB3MM
Sent: Monday, June 26, 2006 3:20 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] cw creation

How does the FCC define CW?

----- Original Message -----
From: "Williams, Barry" <Bnwilliams at varco.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Tuesday, April 26, 2005 18:09
Subject: Re: [TenTec] cw creation

> This particular transmitter is a 1980s synthesized radio using the
> filter method to generate SSB.  I will look up the manual and see how it
> is rated for spurious emissions.  Since it was built for government and
> commercial use, I am sure it had to exceed any applicable FCC
> requirements.  My guess is that it was used for SSB communications
> almost entirely.  It is definitely in the boat anchor category as far as
> weight is concerned, about 50 pounds.  The front panel has 6 knobs that
> are set to frequency, if you need something other than a 100 Hz channel
> you pull out another knob and it allows altering the frequency by a few
> hundred Hz.
>
> The 1958 vintage 32S-1 is the only other rig that I have owned that
> definitely used SSB mode and inserted an audio signal to produce CW.
> That one did have some spurious signals, Collins produced a bulletin
> about converting it from a dual diode mixer to a ring mixer to correct
> some of the problem, then the 32S-3 went back to keying the RF directly.
>
> Seems to me that the only real difference is just how low is the minimum
> frequency signal.  As someone mentioned, if you are generating CW by
> having the DSP generate a 16 kHz signal and mixing it up to the output
> frequency, the filtering to remove the harmonics and opposite sideband
> are the same as if you used a 16 kHz audio signal to a rig operating in
> SSB mode (with the filter offset to pass the audio signal).  It seems
> Collins used 800 Hz for the 32S-1, so the carrier was not far down on
> the filter curve, in addition isolation on the balanced mixer was not
> good.  The opposite sideband did not seem to be the problem, you didn't
> notice the 1600 Hz signal caused by mixing the two sidebands as it was
> covered by the 800 Hz audio caused by the CW/SSB signal mixing with the
> carrier.
>
> I think I remember seeing a design from the early days of SSB which used
> a tuned filter to remove the remaining carrier from the SSB signal.  The
> filter was like the old 455 kHz crystal filters in receivers from the
> early 30s up into the 50s.
>
> Further off subject, an old friend was working a CW contest when someone
> nicely told him that he had a spur about 20 kHz down, he thanked the
> fellow and told him that he would put a receiver down there and work
> calls on both frequencies.
>
> Thanks,
> Barry
>
>
>
> -----Original Message-----
> From: tentec-bounces at contesting.com
> [mailto:tentec-bounces at contesting.com] On Behalf Of Ken Brown
> Sent: Tuesday, April 26, 2005 12:18 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] cw creation
>
> Sounds like an interesting rig.
>
>  If the 1 kHz sine wave has some harmonic content (it is not perfectly
> sinusoidal), this rig could generate as many as five signals:
>
> 1) the desired signal 1 kHz above the indicated frequency
> 2) the second harmonic of the tone generator would still be inside the
> SSB filter and would be a signal 2 kHz above the indicated frequency
> 3) the "carrier" which should be well suppressed, but often is not
> 4) the opposite sideband of the desired signal, 1 kHz below the
> indicated frequency
> 5) the opposite sideband of the second harmonic of the tone generator,
> 2kHz below the indicated frequency
>
> 3, 4, and 5 are supposed to be greatly suppressed if the rig is aligned
> properly. Number two depends on the purity of the tone generator.
>
> If it is a phasing type SSB rig that doesn't use a sideband selecting
> filter, there could be more harmonics from the tone generator, each
> another 1 kHz further from the indicated frequency, and more on the
> opposite sideband too. Phasing type SSB rigs do get out of alignment and
>
> the opposite sideband rejection gets poorer, as well as the carrier
> rejection.
>
> In many cases I think it would be easier to use another BFO crystal and
> unbalance the balanced mixer. There are fewer things to go wrong.
>
> Yes, using the tone modulated SSB transmitter method can be done and has
>
> been done. This is not exactly "a great many rigs", but there are no
> doubt more. Do you know of some more?
>
> >I have an ex-embassy commercial transmitter, the Sunair GSE-924 that
> >injects a 1 kHz sine wave while in USB mode to produce CW.  This is a
> >pretty impressive rig, no cooling fan 30 w AM, 100 SSB and 100 CW.  I
> >have an idea that it was not much used in the CW mode.  They do warn
> you
> >that the transmit frequency is 1 kHz above the indicated frequency
> while
> >in the CW mode.
> >
> DE N6KB
>
> >
> >
> >
>
>
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