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1948 Handbook / 15W Exciter project (310B-1?)




 
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Author Topic: 1948 Handbook / 15W Exciter project (310B-1?)  (Read 954 times)
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no3m
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« on: February 19, 2018, 04:51:18 AM »

Based on information from another forum site posted back in 2007, there is supposedly a "15W exciter" project that resembles a Collins 310B-1 in the 1948 ARRL Handbook.  The 310B-1 has the following tube compliment: 6SJ7 (ECO), 3x 6AG7 Buffers/Multipliers, 2E26 output.  For all I know, maybe the Handbook project only shares the 2E26 output in common with the 310B-1 and the rest of the stages leading up to the output stage differ.

I would like to get a copy (scanned) of the project that is being referenced if it is in fact in the '48 Handbook.

Thanks for any help.

73 Eric
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k7mdo
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« Reply #1 on: February 19, 2018, 06:58:24 PM »

I have the '48 handbook but don't spot a 2E26 transmitter circuit.  I will look again but first pass is no luck.

Tom
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KC2ZFA
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« Reply #2 on: February 19, 2018, 08:00:34 PM »

there are two such exciters in the '47 and '49 editions of the Radio Handbook (not ARRL hb). The file below is a scan from '49.

In the '47 ed there's an 80M vfo which was also marketed by Collins as the 310-C.

* 180219195328-001.pdf (910.42 KB - downloaded 63 times.)
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w8khk
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This ham got his ticket the old fashioned way.


WWW
« Reply #3 on: February 19, 2018, 08:30:31 PM »

Starting on page 58 of the 1949 (12th edition) of the radio handbook, (entire volume downloadable from AmericanRadioHistory site at the following link:) 

http://www.americanradiohistory.com/Archive-Radio/Handbooks/Radio-Handbook-12-1949.pdf

You will find an all-band 15 watt exciter using the Collins PTO using the 2E26 as the output stage.

It also includes a heterodyne crystal calibrator and a separate crystal oscillator to use instead of the VFO.  With frequency measuring equipment available today, these features could likely be eliminated.



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Rick / W8KHK  ex WB2HKX, WB4GNR
no3m
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« Reply #4 on: February 19, 2018, 11:01:13 PM »

Thanks to all for the links and scan.  The exciter in the '49 Radio Handbook appears to be what the poster was referencing.

I'm basically building a 310B-1 homebrew clone that will cover 160-20M, so more than likely will stick with the basic Collins circuit in as far as the buffer/multiplier stages with appropriate changes for the desired bands.  Still not sure if I want to go with a 2E26 or 807 as the output tube.  It will eventually drive a pair of 813s in Class C.

I have the VFO / first buffer and the sidetone circuit built in a temporary chassis.  Since I don't have a Collins PTO unit, I just duplicated the Collins 6SJ7 oscillator circuit with a few changes in the grid circuit.  One wafer of a bandswitch selects bandspreading taps on the oscillator coil, to which the main tuning cap (225pF) is connected and driven by a National NPW-O drive and micrometer dial.  With the current tap points, approx. 250 kc is covered on each band (160 - 20).  A second bandswitch wafer selects fixed and variable padding for each band so that the bottom edge can be set to the same dial reading on each band.  The arrangement is similar to a June 1940 QST article "Single-Dial Frequency Control" (pg. 30), which used a 6K7.  VFO stability is excellent with minimal drift even in the lashed up configuration.

The grid block keying on the first buffer stages works pretty swell.  But the original 0.1MF bypass cap on the grid circuit gave way too soft keying, even worse with the "wave shaping" 0.1MF added in.  I found a total of 0.05MF sounded best and still kept clicks to a negligible level.  Anyone have any experience w/ 310B CW keying characteristics?  Once the first buffer is actually driving something, either the output tube (160) or the next buffer/mult stage (80-20), maybe the grid bypass / shaping value will change for best keying.  Backwave doesn't seem like it will be a problem, but yet to be determined until the exciter is permanently constructed and housed.

Fun project so far, anxious to start laying it out on a permanent chassis soon.


* 310B-clone-1.JPG (91.86 KB, 600x437 - viewed 91 times.)
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KA2DZT
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« Reply #5 on: February 20, 2018, 12:32:33 AM »

What National receiver do I see in the background??  Good luck with your project.  I had a Collins 310 that was a basket case.  I reduced it to parts and pieces many years ago.  I think the PTO is around here somewhere but haven't seen it in years.

Fred
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no3m
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« Reply #6 on: February 20, 2018, 01:15:57 AM »

RX is a HRO-5TA1.  It was completely restored inside and out by a couple owners back.  Doesn't get used enough, but has been at the center of our OT Field Day setup the last couple years with various breadboard and wooden rack style transmitters (latest was a 89 ECO, 42, 802 exciter driving PP 814s).

I hope the 310 isn't a basket case by nature! hi  Would be a lot of work to find out it's a lemon design, but it seems to be standard fair for the era.  So far my imitation VFO + 1st buffer sounds very good, even on the harmonics.  Only start to notice a slight chirp on 20M.  Haven't decided if it'll ever see AM phone, which will require a little more band coverage to hit the waterholes.  300kc per band should do it, either by moving the coil taps 1T towards the grid end for each band or a larger value tuning cap.
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nq5t
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« Reply #7 on: February 20, 2018, 04:25:03 PM »

Starting on page 58 of the 1949 (12th edition) of the radio handbook, (entire volume downloadable from AmericanRadioHistory site at the following link:) 

http://www.americanradiohistory.com/Archive-Radio/Handbooks/Radio-Handbook-12-1949.pdf

You will find an all-band 15 watt exciter using the Collins PTO using the 2E26 as the output stage.

I recall something nearly identical to this changing hands on eBay during the last couple of years.  It had the look of some sort of Collins prototype, but was clearly home brew and very well built.
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