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Author Topic: Heathkit SB400 versus 401  (Read 25213 times)
KD4SBY
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Posts: 269




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« on: September 18, 2011, 08:28:25 AM »

I just obtained a Heatkit SB400 with no manual, but have the schematic for the SB401. Anyone can tell me what the differences are between the two versions?
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W5RKL
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« Reply #1 on: September 19, 2011, 10:39:01 AM »

The obvious difference is the front panel "FREQ CONTROL" switch on the SB-401 that is not present on the SB-400. The FREQ CONTROL switch on the SB-401 controls which LMO is used to
control the transmitter. The "UNLOCKED" position, the transmitter controls the transmitter frequency. The "LOCKED" position the receiver controls both the receiver and transmitter
LMO output frequency.

Another difference is the SB-400's 8 het osc crystals were "standard" with the SB-400 but they were an "option" with the SB-401. Without the 8 heterodyne oscillator crystals,
the transmitter must be connected so the receiver's LMO provides the LMO frequency otherwise the transmitter will not work.

There are other minor circuit changes but basically, the SB-400 and SB-401 were the same transmitter.

The SB-400 and SB-401 LMO's (VFO) operate over a frequency range from 5.500Mhz (bottom of all bands) to 5.000Mhz (top end of all bands).

The 8 het osc crystals are the same crystals used in the HW-100, HW-101, SB-100, SB-101, SB-102, SB-300, SB-301, SB-303, SB-400, and SB-401 transceivers, receivers, and transmitters.
They all are interchangeable among these individual transceivers, receivers, and transmitters.
 
73s
Mike
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KD4SBY
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Posts: 269




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« Reply #2 on: September 20, 2011, 06:14:26 AM »

Thanks Mike. Without knowing it, it is difficult to see it from pictures. Since I want to use it as a TX by itself, the 400 would have been then my choice anyway.
BTW I have all the xtals (11 of them)for the series, just in case.
Anywhere that you know off that I can find a manual for the 400 for free or a reasonable fee?
Thanks.
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N2EY
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Posts: 5079




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« Reply #3 on: September 21, 2011, 06:23:32 AM »

Without the 8 heterodyne oscillator crystals, the transmitter must be connected so the receiver's LMO provides the LMO frequency otherwise the transmitter will not work.

I think you meant:

"Without the 8 heterodyne oscillator crystals, the transmitter must be connected so the receiver's heterodyne oscillator provides the heterodyne frequency otherwise the transmitter will not work."

73 de Jim, N2EY
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N4NYY
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« Reply #4 on: September 21, 2011, 02:30:57 PM »

Quick question. I saw one of these at our hamfest. What is the difference between the SB-4xx and the SB-1xx ?
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KQ6EA
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« Reply #5 on: September 21, 2011, 03:14:14 PM »

The 4xx are transmitters.
The 1xx are transceivers.
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N4NYY
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Posts: 5224




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« Reply #6 on: September 21, 2011, 07:04:36 PM »

Quote
The 4xx are transmitters.
The 1xx are transceivers.

Holy crap. He only had one. What are the receivers? I should have known this before, as I was tempted. Good thing I did not bite.
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W5RKL
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« Reply #7 on: September 21, 2011, 07:40:40 PM »

Yes, Jim, N2EY, you're right. My mistake. I must have been thinking one thing but typing another.

N4NYY, the separate Heathkit receivers were the SB-300, SB-301, and the SB-303, These were ham band only receivers.

The SB-300 and SB-301 are vacuum tube receivers while the SB-303 is all solid state.

Any of the above receivers will work with either the SB-400 or SB-401 transmitter (see the manuals for "transceive" operation).

The antenna change over relay is located inside the transmitters so you do not need an "external" relay for relay and mute switching between receive and transmit.

73s
Mike


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N4NYY
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Posts: 5224




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« Reply #8 on: September 21, 2011, 07:43:33 PM »

Quote
Yes, Jim, N2EY, you're right. My mistake. I must have been thinking one thing but typing another.

N4NYY, the separate Heathkit receivers were the SB-300, SB-301, and the SB-303, These were ham band only receivers.

The SB-300 and SB-301 are vacuum tube receivers while the SB-303 is all solid state.

Any of the above receivers will work with either the SB-400 or SB-401 transmitter (see the manuals for "transceive" operation).

The antenna change over relay is located inside the transmitters so you do not need an "external" relay for relay and mute switching between receive and transmit.

Lesson learned. Only buy what you are sure of. The thing that caught my eye was that it was close to being a duplicate of an SB-101. At the last second, I saw 401.
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N2EY
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« Reply #9 on: September 22, 2011, 07:05:38 AM »

The thing that caught my eye was that it was close to being a duplicate of an SB-101. At the last second, I saw 401.

The whole family (SB-100, SB-101, SB-102, SB-300, SB-301, SB-400, SB-401, HW-100, HW-101) share a LOT of parts. The SB-110 (6 meters) and SB-303 (solid-state rx) somewhat less. All sorts of hybridization and cannibalization are possible. Hangar queens could keep you on the air a very long time.

To make it even more of a sporting course, the VFO in the Tempo One/FT-200 covers the same range (5.0 to 5.5 MHz) as the Heath LMO/VFO. If you're really up for a project, you could transplant a Tempo One VFO into an HW-101/100 and get a much nicer dial and RIT.

Perhaps the ultimate tribute to the Heath SB/HW family was the ATR-166, a homebrew article in QST about 1971. It was a transceiver covering 160 through 6 meters (no WARC, though) using the Heath heterodyne scheme, filters, etc. Nice Eddystone 898 dial, too - but plug-in band modules!

73 de Jim, N2EY
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W5RKL
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Posts: 1113




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« Reply #10 on: September 24, 2011, 07:38:20 AM »

The Heathkit SB line has the model number directly above the LMO knob. Having said that, I have an SB-401 where the SB-401 tag was missing. Therefore, it's possible
the model label could be missing.

The transceivers have a "PHONES" and "MIC" socket on the lower left corner of the front panel and the transmitter has a "Mic" socket on the lower right.

The meters are different on the transmitter and the transceiver. The transmitter meter has one white arc while the transceiver meter has 2 white arcs.

The receivers (SB-300 and SB-301) look the same as the transmitters (SB-400 and SB-401). You can tell the difference between the receiver and transmitter
rather quickly by the location of the meter. The meter on the receiver is located on the "left" while the meter on the transmitter is located on the "right".

73s
Mike
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KD4SBY
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Posts: 269




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« Reply #11 on: September 27, 2011, 12:19:57 PM »

Update - I got myself a SB-301. As I like to use it with the SB-400 as a Transceiver, I have to figure out how to connect the two together to accomplish that. I still do not have the manual for the 400, and I am wondering if originally the two were capable of being connected that way. Anyone knows that? I know that the 401 was equipped to do so.
BTW I still like the old tube type SB/HW series. I was able to do a side by side receiving comparison with some newer Icom and Kenwood equipment with the same functional capabilities, and I could hear (or not hear) the same stations in either one of them. the difference was only that one was a tube type and the other was solid state, and thus by definition was more efficient than the tube type. Grin
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W5RKL
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Posts: 1113




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« Reply #12 on: September 28, 2011, 06:00:17 AM »

Update - I got myself a SB-301. As I like to use it with the SB-400 as a Transceiver, I have to figure out how to connect the two together to accomplish that. I still do not have the manual for the 400, and I am wondering if originally the two were capable of being connected that way. Anyone knows that? I know that the 401 was equipped to do so.
BTW I still like the old tube type SB/HW series. I was able to do a side by side receiving comparison with some newer Icom and Kenwood equipment with the same functional capabilities, and I could hear (or not hear) the same stations in either one of them. the difference was only that one was a tube type and the other was solid state, and thus by definition was more efficient than the tube type. Grin

Yes the SB-301 will operate in "transceive" with the SB-400.

If the SB-301 receiver and SB-400 transmitter have never been connected in transceive, there are some initial circuit changes/adjustments that must be made first before transceive
operation can take place in order for the receiver and transmitter to operating on the same frequency. There are 3 cables that are required to connect the SB-301 and SB-400 together
to operate in transceive. All of this is contained in the manuals.

If you plan on operating the SB-400 transmitter as a separate transmitter, then the 8 het osc crystals must be installed in the crystal sockets. Without the crystals the transmitter will not work.

When troubleshooting, aligning, or simply setting the SB-301 and SB-400 transmitters up for transceive operation you should always have the manuals for both the receiver and transmitter.
You can purchase the manuals from various manual websites, one I recall is w7fg.com. You can purchase the manuals from w7fg.com at the following prices plus shipping

SB-301 = $32.00
SB-400 = $32.00


73s
Mike
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KD4SBY
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Posts: 269




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« Reply #13 on: October 01, 2011, 06:29:18 AM »

Thanks fellows. I am have ordered the manuals. Rather pricey considering that they were originally $2.00 !
W5RKL - Just curious, before I will receive the manuals to look at it, do I understand from your explanation as to joining the two together, that once you make the arrangement to use it as a  Transceiver, you can not use the SB400 anymore as a separate TX without having to readjust things? The SB400 I have has all the Xtals as they came with the kit.
Also, do you know that if you want to use them not linked, but together, how to make sure that you are on the same operating frequency in both of them? Is there a procedure for that?
Thanks.
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W5RKL
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Posts: 1113




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« Reply #14 on: October 04, 2011, 03:11:25 PM »

W5RKL - Just curious, before I will receive the manuals to look at it, do I understand from your explanation as to joining the two together, that once you make the arrangement to use it as a  Transceiver, you can not use the SB400 anymore as a separate TX without having to readjust things? The SB400 I have has all the Xtals as they came with the kit.
Also, do you know that if you want to use them not linked, but together, how to make sure that you are on the same operating frequency in both of them? Is there a procedure for that?
Thanks.

Yes you can use the SB-400 as a separate transmitter but you will have to reconnect the internal LMO cable to the rear of the LMO. The SB-400 does not have the front panel "LOCK" and "UNLOCK" frequency control switch the SB-401 has. You have to "manually" change the LMO cables inside the SB-400 when switching between transceive and separate operation. This takes about 5 seconds to do if you have the SB-400 LMO cables connected as described in the SB-400 manual.

To put the SB-400 and receiver on the same frequency, it depends on what mode you will be using. For CW or sideband you use the Function switch "SPOT" setting. This setting turns on all circuits except the final amplifier, allowing you to "talk yourself" on frequency.

For sideband, you place the SB-400 Mode switch to USB or LSB and the Function switch to "SPOT". While speaking into the microphone in a normal tone of voice, adjust the SB-400 LMO until you hear your normal voice in the receiver speaker. Once this is completed, you set the SB-400 Function switch to TRANS and your on frequency and ready for sideband transmissions.

For CW you do the same thing except the mode switch is in CW.

Again, after you do the above adjustments, you must place the Function switch to "TRANS", regardless of the mode you are using. If you forget to do this or place the Function switch to "TRCV", you won't be transmitting on the air so don't forget to do this. In "TRCV" the SB-400 is assuming you are getting the oscillator signals from the receiver and even though the SB-400 relays will click, you won't be transmitting on the air. The only time you use the Function switch "TRCV" setting is when you are "transceiving" with the Receiver controlling the oscillator frequencies. This is all discussed in the SB-400 manual.

Once you get the hang of it, it won't take you long to put the SB-400 on frequency, either in CW or sideband. I have done it enough times that it takes me less than 10 seconds to adjust my SB-400 or SB-401 LMO on frequency whether on CW or sideband.

If your microphone element is wired through the PTT button you may have to press the PTT button for this feature to work. I wire my microphones straight through to the plug, bypassing the PTT switch. I never use VOX so VOX is not an issue with the microphone wired this way.

73s
Mike
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