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John KC0G · 20th Apr 2016, 7:10 pm

Hello David et al

You comments about the weight of the H2900 make me think about equipment density being measured in kg per U of rack height. I have had to pull audio power amps, which would measure quite highly, out of racks.

I have been reading Sosin's article on the H2900. (see post #35) It paints broad pictures of the technical detail but only goes so far. Pat Hawker, G3VA, wrote a nice summary in the RSGB's Radcom, Feb 1970, pp 92-93. He did include the block diagram, which does show a filter for separating the carrier at IF, but does not show how it is regenerated. He also noted Sosin's use of the term "roofing filter". Was that term in common use at the time (1970)?

G3VA briefly mentioned the frequency synthesizer, saying that it had little connection with amateur equipment. It uses a pulse subtraction technique, and looks to me as though it is a frequency, not phase, locked loop. It may be an extension of Sosin's earlier work, ie patent no. GB1085866,, also granted as US3349338, and elsewhere, with a priority date of Feb 3rd, 1965.

I note your comments about the wire-wrapping. The whole radio was designed not to have plug and socket connectors. Marconi were seriously concerned about reliability in solid-state equipment, in part due to soaring component counts. This is what I took away from a brief glance at:
....J.V. Beard, Factors Affecting Reliability, Point-to-Point Telecommunications, Vol. 13, no. 4, October 1969, pp 157-163
I have not read the article in detail.

The survey of communications receivers by Beard, and Sosin's article on receiver reception failure (see post #35) really help put the H2900 into context. The only other receiver with 1Hz tuning increments was a Racal set, and I don't know which one. The Racal RA1772 and two other receivers were shown as tuning in 10Hz increments, and many of the others tuned in 100Hz increments. The price was some 20% less than the MST point-to-point receivers, but ca. 4 times that of the Racal RA1772., and ca. 9 times that of the price reference, which is assumed to be the Racal RA17L.

it makes me wonder just how many of the H2900 series were sold. The market place can be very cruel to products which might be technically brilliant, but are simply too expensive. The Drake TR-7 amateur radio transceiver is but one example.

73 John KC0G

20th Apr 2016, 7:10 pm	#42
John KC0G Hexode Join Date: Mar 2009 Location: Minneapolis, Minnesota, USA. Posts: 278	Re: ISB Receivers Hello David et al You comments about the weight of the H2900 make me think about equipment density being measured in kg per U of rack height. I have had to pull audio power amps, which would measure quite highly, out of racks. I have been reading Sosin's article on the H2900. (see post #35) It paints broad pictures of the technical detail but only goes so far. Pat Hawker, G3VA, wrote a nice summary in the RSGB's Radcom, Feb 1970, pp 92-93. He did include the block diagram, which does show a filter for separating the carrier at IF, but does not show how it is regenerated. He also noted Sosin's use of the term "roofing filter". Was that term in common use at the time (1970)? G3VA briefly mentioned the frequency synthesizer, saying that it had little connection with amateur equipment. It uses a pulse subtraction technique, and looks to me as though it is a frequency, not phase, locked loop. It may be an extension of Sosin's earlier work, ie patent no. GB1085866,, also granted as US3349338, and elsewhere, with a priority date of Feb 3rd, 1965. I note your comments about the wire-wrapping. The whole radio was designed not to have plug and socket connectors. Marconi were seriously concerned about reliability in solid-state equipment, in part due to soaring component counts. This is what I took away from a brief glance at: ....J.V. Beard, Factors Affecting Reliability, Point-to-Point Telecommunications, Vol. 13, no. 4, October 1969, pp 157-163 I have not read the article in detail. The survey of communications receivers by Beard, and Sosin's article on receiver reception failure (see post #35) really help put the H2900 into context. The only other receiver with 1Hz tuning increments was a Racal set, and I don't know which one. The Racal RA1772 and two other receivers were shown as tuning in 10Hz increments, and many of the others tuned in 100Hz increments. The price was some 20% less than the MST point-to-point receivers, but ca. 4 times that of the Racal RA1772., and ca. 9 times that of the price reference, which is assumed to be the Racal RA17L. it makes me wonder just how many of the H2900 series were sold. The market place can be very cruel to products which might be technically brilliant, but are simply too expensive. The Drake TR-7 amateur radio transceiver is but one example. 73 John KC0G Last edited by John KC0G; 20th Apr 2016 at 7:30 pm.