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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 24th Apr 2019, 6:45 am   #81
Radio Wrangler
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Default Re: ISB Receivers

The term ISB best fits the case where the transmitter applies different information to the two sidebands, or there may even be two separate SSB transmitters sharing a carrier source.

If the transmitter applies the same information to both sidebands, and a receiver chooses which sideband to reproduced based on, say, interference or fading, then 'sideband diversity' is a good description. The difference lies in the intent of the system, the TX may be a plain old DSB AM job with full, reduced or suppressed carrier and the receiver may be one capable of fully independent sideband reception.

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Old 24th Apr 2019, 2:58 pm   #82
John KC0G
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Default Re: ISB Receivers

The GE YRS-1 was the commercial adapation of the single-sideband adapter which was published by Don Norgaard in QST, July 1948. See pages V-35 to V-40 of the GE Sideband Handbook at http://the-eye.eu/public/Books/Elect..._1961_text.pdf

While on the subject of sideband convertors. there were a number made here in the USA in the 1950's. See http://www.navy-radio.com/rcvr-ssb.htm Perhaps some of these convertors were commercial designs which were adopted by the US military. Some, probably not all, offered ISB capability. Several were made by TMC (Technical Materiel Corporation). You may find further information at http://www.tmchistory.org/

See also the HF Diversity Receiving Systems page at the same site. Some systems effectively had ISB capability. See also the the HF & MF receiver page, and the link to the R-1051 page. My understanding is that the R-1051 was built for the US Navy. It had ISB capability. It was also incredibly expensive. The early General Dynamics versions reportedly cost over the $20,000, and the last Stewart-Warner version around $50,000.

73 John

Last edited by John KC0G; 24th Apr 2019 at 3:13 pm. Reason: correction
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Old 21st May 2019, 2:39 am   #83
Synchrodyne
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Default Re: ISB Receivers

John, thanks for the links – plenty to consider there.

Quote:
Originally Posted by Radio Wrangler View Post
If the transmitter applies the same information to both sidebands, and a receiver chooses which sideband to reproduced based on, say, interference or fading, then 'sideband diversity' is a good description. The difference lies in the intent of the system, the TX may be a plain old DSB AM job with full, reduced or suppressed carrier and the receiver may be one capable of fully independent sideband reception.
A good summary of sideband diversity reception of DSB transmissions was given in the POEEJ 1952 October article on SSB/ISB, as follows:

“Single-sideband Reception of Double-sideband Telephony Transmissions.

“When a d.s.b, transmission is received in the normal d.s.b. type of receiver, severe degradation of the quality due to non-linear distortion often occurs if selective fading is present, as already discussed. The distortion due to selective fading can be overcome by receiving the d.s.b. transmission in a single-sideband receiver, in which one sideband only is selected and is demodulated against a stable high-level carrier, either the original carrier after filtering, amplification and limiting to remove fading and noise, or a local carrier.

“Another advantage of this method of receiving a d.s.b. transmission is evident when an interfering signal falls in one of the sidebands of the transmission. Such an interfering signal appears in the audio-frequency output of the receiver if d.s.b. reception is employed, but with an independent-sideband receiver it is possible to eliminate the interfering signal by selecting the sideband which is clear of interference.

“In the absence of interference an independent-sideband receiver can be used to receive the two sidebands of a d.s.b. transmission separately. The two audio-frequency outputs, each carrying nominally the same intelligence, will have undergone attenuation of some frequency components relative to others, but the attenuated components are not necessarily of the same frequency in both cases. Thus, by suitably combining the two audio outputs, a frequency-diversity system is obtained which results in a steadier audio output with less frequency-selective fading than is possible with normal d.s.b. reception."

One could say that the Crosby exalted carrier DSB demodulation system (which was included on at least the early Crosby ISB assemblies) and the GE YRS-1 (in DSB mode) automatically provided the frequency-diversity system mentioned in the GPO article, without the need for any sideband recombination circuitry On the other hand, adding a simple recombination circuit to a regular ISB receiver was probably the simplest route. As far as I know, Radio New Zealand (or NZBC as it then was) simply used a fader between the two sideband outputs of its Marconi HR21 ISB receivers at its Quartz Hill facility. I understand though that the Costas loop is even better for demodulating DSB under selective fading conditions than say a PLL. This is attributed to the fact that the Costas Loop, in using the sidebands to recreate the carrier, follows the short-term phase variations of the latter whereas the PLL provides a flywheel effect.


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