Rate Your BC Transmitter

[flintstone mop]

I thought this might be an interesting thread to give folks an opportunity to rate their BC transmitter. There must be many Ham ops with BC transmitters on the air  on the Ham bands these days.
The Ratings would be for: Ease or difficulty of converting to the Ham bands
                                   Audio quality and ease of obtaining over 100% pos peaks
                                   The electronic design. Over-designed under designed
                                   Pretty box or an ugly box
                                   Converted to other bands beside 160M

If there are other ratings please feel free to add your comments.

Fred

[k4kyv]

Size and weight.

[N3WWL]

Yes to all the above on my old Raytheon RA-250. Easy to achieve over 100% positive peaks, totally over-desiged, and easily converted to 75. The only questionable one would be "pretty or ugly".  Beauty is in the eye of the beholder.  The old boy sure could have used some glass.

[k4kyv]

My Gates BC1-T has pretty good audio, but I think my homebrew rigs sound better.  It was built with "cheap" in mind, but it works reliably.  It took some work to convert it to a usable ham rig, and it only works on 160.  I would say it was under-designed, given the burnt spots on the driver circuit boards, and a measly pair of 807's driving a pair of 833A's.  It will modulate over 100% positive now that I added some series power resistors it the +HV to the rf final, while keeping full voltage on the modulators.  It is pretty massive in size and weight by ham radio standards, but a little on the light and compact side by broadcast standards.  But I have to say it is about the ugliest box I have ever seen for a broadcast transmitter.  Looks  more like a soda machine or refrigerator than a radio transmitter.  But I can't look a gift horse in the mouth.

[k7yoo]

I agree with Don on the Gates. I always refer to them as the "Globe King" of the broadcast world: kinda flimsy, not real purty, but they sound good.

I suppose the 20V series is my favorite because they are easy to convert to other bands (especially the 20V3), and will fit in a mini van. I must admit to going nuts and running the 21E so that I could be a player in the weight/volume category. For that you need the mini van and a trailer.

For classic art deco looks the WE or old RCA units are hard to beat, but conversion ends up becoming total redesign. My take on these is they are a great looking box for a homebrew transmitter.

[flintstone mop]

I had a McMartin BA1-K and it was a nice 80's transmitter with woodgrain cabinet. The 4-500's were fortunately strong tubes and made its rated power and modulated pos 125% easily. Better than a 20V2 I owned at one time.
The RF exciter / oscillator was very strange and used a divide by circuit to derive the on-air freq ( calculated weird xtal freqs), so I got a plastic radio and antenna tuner to drive the RF finals with 40ma of grid drive.
The modulator had no scrote for low end. The mod transformer was a tinny light thing encased in oil.
I was able to "bandswitch" the TX up to 40M with no instabiltiy.
The P.S. was light, but managed to handle full load with pretty good regulation.

Fred

[Jeff W9GY]

Got a unmodified Gates BC1-G sitting in the garage undergoing restoration.  Hopefully it will be in the shack and on-air (at least 160M) by year's end.  Yes, like Don's "T", it uses 807's for drivers and the glass pc boards show evidence of getting pretty hot near the power resistors.  A small fan aimed at the boards and some new resistors ought to solve that issue.

Obviously, too early to comment on performance, though.  Stay tuned.

[Opcom]

Looks  more like a soda machine or refrigerator than a radio transmitter.  But I can't look a gift horse in the mouth.

That was to keep the salespeople from messing with it. Sales and Management are supposed to have free food catered in and should not lower themselves to paying for sodas and using a communal refrigerator..

...............

RCA BTA-250L

A+ for nice looks even if you can't see the tubes. the cabinet is 100% quality and it has recessed lighting via a "lumiline" lamp over the knobs.

A+ for tuning as except for the MO, it is tunable from the front panel including loading and neutralization.

I can't say ease of for conversion to 160. The MO will go above the BC band but I have not fired the transmitter up yet. It can be done I am told.

Can't say for converting to other ham bands. I would say yes, if you were willing to remove much of the original tuning gear and replace with whatever but there are not enough knobs to do the driver and final both. I would not like to drill holes in that..

[k4kyv]

The Gates BC1-F is a totally different matter.  It is massive. 3000  lbs to be exact.  The cabinet is double-wide, like two BC1-T's side by side.  The mod iron weigh a couple of hundred pounds each.  A pair of 845's drive the 833A's in the modulator and it uses an 813 to drive the RF 833A's.  And it uses real off-the-shelf EF Johnson 833A sockets, not those chintzy in-house made jobs using a strip of bakelite and connectors made from pieces of aluminium turned out on a lathe.  It also has turns counters on the rotary inductors, and a dozen or so panel meters, instead of just four.

Comparing the 1-T to a 1-F would be about like comparing a Corvair to a Cadillac. 

[W2XR]

Yup, I agree with Don on this one, and he and I have discussed this on the air previously.

I personally think the Gates BC-1F was probably the best plate-modulated BC rig I had ever heard, or had the good fortune to work on. I maintained the one at WGSM/740 on a part-time basis during the early '70s when I was in college. That rig had that classic "jukebox sound"; a full, rich, powerful sound, compared to the Gates BC-5P they had as the prime daytime rig. It was a pleasure to listen to it on the off-air monitor in the transmitter building, cranked up full tilt through some good quality tube amplifier they had there. The BC-5P sounded like garbage by comparison, with it's 23 dB of negative feedback between the modulator and audio driver. The BC-1F had only 6 dB of voltage feedback in the modulator/driver section, and much better quality iron in the audio signal path, not to mention an audio circuit of superior design. The mod reactor in the BC-1F was 60 hys, if I recall correctly. Most later Gates 1KW-class BC rigs used smaller 32 hy reactors. The BC-1F mod transformer weighs in at around 200 lbs; I cannot move the one here in the W2XR basement myself, whereas I can easily lift the BC-1G mod trannys I have.

I liked the sound of the BC-1F so much that I built the audio driver and modulator sections in my homebrew rig exactly like that of the BC-1F; a pair of 6J7 voltage amplifiers, a pair of 6J5s as pre-drivers, a pair of push-pull class A 845s with self-bias as the audio driver stage, and a pair of push-pull class B 833As with 6 dB of global negative feedback for the modulator. Instead of the massive and unwieldy BC-1F modulation transformer and modulation reactor, I use the transformer and reactor from a Gates BC-1G, as they were MUCH easier to install on a size and weight basis.

I believe the audio circuitry in the Raytheon RA-1000 is virtually identical to that of the BC-1F, and the RF section is very similar, too. I recall the RA-1000 uses a pair of 813s (!!!) to drive the pair of 833As in the HPA, whereas the BC-1F used a single 813. Suffice it to say, a single 813 for that application is still overkill.

I wish I had the room for a BC-1F here in the shack, but it is a huge package for a 1000 watt-class BC rig. My recently acquired TMC GPT-750 is big enough, along with the other BAs I have. I parted out a beautiful BC-1F a number of years ago, as the rig was simply too large to be removed intact from the transmitter room of the station it was located in; the station had expanded the administrative office section around the transmitter over the years, rendering removal of the rig an impossiblity. The Chief Engineer said to me, "take it apart then, or we'll pull it apart and put it in the dumpster". Suffice it to say, myself and a buddy of mine were there the following Saturday morning, tools in hand, and I hauled everything within that beast home. The only thing left was the massive two-bay cabinet, and a Sawz-all took care of that. Broke my heart, but a ham has to do what a ham has to do.....

73,

Bruce

[John K5PRO]

You can see the aforementioned BC1T and BC1F models from Gates Radio here:
http://louise.hallikainen.org/BroadcastHistory/index.php/GatesRadioCompany

The 1F advertisement is located in the 1950 Gates catalog that I uploaded there some time ago. I agree that the 1F was the last of big Mohicans from Gates, as from the T on, they used the 807 drivers and lightweight iron. Of those designs, all similar in basic lineup, the G was one of the better designs, and not so unattractive. The H, which I have in unconverted form, was a cheapened repackaged G. Harris called this Value Engineering. Smaller box is the main sell feature and the 1H1 had solid state audio driver. 

I parted out a RA1000 five years ago in Roswell, NM. It differed from the rest, in that all the RF and audio chains were push-pull throughout. The pair of RF 813s drove a pair of 833s, and all of the tuning used split stator air variables. This proved to be a weakness in the PA output as the capacitor plates were arced up and melted in the one I found.  It had a beautiful inductor with a variometer link inside for the coaxial output connection to antenna. These make a fine basis for a balanced antenna tuner - what I am planning to do with mine. The RA1000 was not a piece of beauty but it was built big and heavy.

[John K5PRO]

Continental 314R1/Collins 828C1:
http://www.jtml.info/314R1/314R1.html

Ease or difficulty of converting to the Ham bands -
Difficult, requires redesign of RF driver stage from BJT to MOSFETs, final PA changes minor
Has been done by at least one ham, but I haven't attempted it yet.

Audio quality and ease of obtaining over 100% pos peaks -
High quality audio, out to 9 KHz, no modulator iron, nearly "DC coupled" audio, easily does 130% positive

The electronic design. Over-designed under designed -
Overdesigned, many innovative features, uses three 3-500Z triodes, one as a PDM switchtube, vacuum variable tuning, no choke in power supply (just BIG capacitor), high quality audio input stage
weakness is the switch tube driver card, prone to failure, keep spare transistors

Pretty box or an ugly box
Attractive, compact, later models had viewing window for tubes

Converted to other bands beside 160M
Can be done if new driver is built right. Would need to examine and possibly replace the RF bypass capacitors on the cathode of the final tubes, for higher than 160 meter operations.

[John K5PRO]

Harris BC1H1
http://www.jtml.info/BC1H1/BC1H1.html

Ease or difficulty of converting to the Ham bands -
Easy, similar to BC1G and T conversions

Audio quality and ease of obtaining over 100% pos peaks -
Similar to 1G, response to 7 KHz, peaks MAYBE 115% if careful

The electronic design. Over-designed under designed -
Same old design, 807s driving 833s for RF, audio is solid state up to 833s
Underdesigned for some components. Built in dummy load in cabinet.

Pretty box or an ugly box
One of the more attractive Gates/Harris boxes of this design, similar to 1G except more compact and no screen in front. 833s laid out on bakelite bar across front behind window, bar tends to warp with time and heat.

Converted to other bands beside 160M
Can be moved to 75 meters at least, paying attention to long leads to 833 grids and cathodes.

[flintstone mop]

In my early years of discovery of the A.M. mode, the HUZMAN and I went to some radio station near West by god Virginia. and they had a BC1-F there that I was going to purchase.

The station folks kept waving us away as we pulled up to the TX site. Turns out that the pickup truck we had would never been able to bear the load of that beast. It was a lot of transmitter for only 1KW.

My lame excuse for not going through with the deal was that no one would ever return my phone calls asking for dimensions of the beast. I guess I cudda been more resourceful and dug up the info from the Internet. This was a middle/late 90's time.
Fred

[KL7OF]

I converted a Collins 300-j to 75 meters.4-125s x 4-125s .......changed the tank coil ...I used the "L"coil that I removed from my BC1G ...I changed the Tune cap from a 350 pf to a 175pf...I rewound the  oscillator and driver coils and clipped out some "C" in those circuits..Xtal control ..The Audio circuit remains stock.   The 600 ohm input is fed with a behringer box..120% mod peaks easy when the out put level is set at 300 watts...I'm told this one is the best sounding of my transmitters...Large shiny art deco chrome and glass box with the big Collins logo on the front..Tubes in the window... mercury vapors giving off the bluish glow..4-125s slightly orange...Very cool....I also have a the aforementioned Bc1g on 160 meters...Much modified with some 5 kw mod iron ...Lotsa scrote, dependable,ugly...Lastly I have
a much modified RCA BTA1-S that now uses triode connected 813s as modulators for the 4-400s and the tank circuit changed to Pi network from slug tuned coil...RF oscillator- driver is homebrew tube type...Speech amp is homebrew 6l6's with some feedback..Box is a standard width rack with sheet metal panels mounted on the side to make it look bigger...Holes have been cut in the door for tube viewing, blower is noisy,Easily makes 130%.... side panels vibrate when the iron starts talking.....Kinda ugly squared off corners...I put a "Nipper" logo on it and call it the "Bad Dog"
I would like to have a McMartian 4x1 rig someday......

[k4kyv]

In my early years of discovery of the A.M. mode, the HUZMAN and I went to some radio station near West by god Virginia. and they had a BC1-F there that I was going to purchase.

The station folks kept waving us away as we pulled up to the TX site. Turns out that the pickup truck we had would never been able to bear the load of that beast. It was a lot of transmitter for only 1KW.

My lame excuse for not going through with the deal was that no one would ever return my phone calls asking for dimensions of the beast. I guess I cudda been more resourceful and dug up the info from the Internet. This was a middle/late 90's time.
Fred

I would have rented a room in a cheap nearby motel and gutted the transmitter, and hauled all the iron and other components and stashed them in the motel.  Then I would have used a Sawzall or sheet metal blade in my Skillsaw and cut up the cabinet into sheet metal panels.  As much of the stuff as the truck would have held would have  gone home with me, and if I couldn't have loaded the sheet metal salvaged from the cabinet, it would have gone to a metal recycler and then I would have loaded up the transformers, tubes, coils, meters and other goodies and carried them home.

[W7IXZ]

I have several of the Gates 1 KW rigs, with one on 160. It was easy to convert to 160 and does a good job.  The one I have on the air is one with the 6BG6 tubes in place of the 807's.  My plan is to do one more conversion by using my DX 100 as a driver to provide more RF drive to the 833 finals.  I plan on running the DX 100 6146 plate supply through the driver winding on the Gates modulation transformer to modulate the 6146's like the original Gates modulating the 807 drivers.  I would use the audio section as is in the Gates, using my Gregg Labratories 5 band limiter/agc box.  One of my Bauers is converted to 80 using a Johnson Ranger as driver.  I installed a B&W 80 JCL coil and dual capacitor for the grid circuit link coupled to the Ranger and added a 6Y6 clamp tube to the 4-400 finals.  I am still fiddling around with my RCA BTA 1M which is much harder to get up and running.  I still have three BC1T's and one Bauer 707 in the barn.  To me they are all beautiful!
I started as a BC Chief in 1957 right out of high school and retired from KXL in 2003.