Eric writes:

Did you guys see that #44261 just sold on eBay for over $2500!=C2=A0 I was =
amazed to say the least! I really had no idea they where worth that much.

On eBay, never equate selling/listing price with 'worth'.

For an example, look at the absolutely stupid listing prices that
some jackass in Australia has on his/her Drake and other listings.

There is also a character on Vancouver Island who regularly lists
old Swan gear, and occasionally Drake gear, for completely absurd
prices. And his shipping charges are even more insane. The listings
do come and go, so maybe there are people out there stupid enough
to pay those ridiculously inflated prices. Or maybe he just hauls
the stuff to the dump. What I can't figure out is how he acquirs
it all in the first place. He is not exactly located in the middle
of a metropolis.

--lyndon

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Eric!

Congrats on the late S/N TR4CW/RIT!!

This, according to Bill Frost,? was probably the last TR-4C built. Back in the Seventies, Drake records indicated that the last two built were shipped to Henry Radio in Los Angeles. This one had the highest S/N of the two. I am the original owner.

Cheers!

de Benton? w4jba

On Tue, Apr 4, 2023 at 10:30 AM, John K5MO wrote:

Sorry, if this has been posted before, but there's an interesting photo of Drake gear in a commercial setting in the photo at the bottom of this page:





I remember hearing WLO yrs ago. Looks like they used both 4 line an 7 line equipment

John K5MO

These are really great pics!
Wonder how long the 4 line continued to be operated after the 7 line was launched in commercial settings?
Probably the same for any other tube equipment.? Gradually depending upon budgets etc.

I have #45407 that just got back from a trip to see Ron Baker in January. Looking thru this thread I think that is the latest serial number that has been listed.??



It works great and I am really happy to have it.? Picked it up at a garage sale in 2019, and in fact I didn't even realize it was a RIT version until I got it home. I had just thought it was a CW version.?Also got a set of B line twins at same sale, and of course two sets of AC-4 and MS-4.? All in like new condition.? He had an L4B for but had no power supply so I passed as he really wanted to much for it.? He told me that he had listed it on Facebook marketplace for over a year and that I was the first one to come see it that even knew what it was.? I just happened to see all the Drake stuff on a table in the driveway as I drove by and had to stop.? Boy am I glad I did!

Did you guys see that #44261 just sold on eBay for over $2500!? I was amazed to say the least! I really had no idea they where worth that much.?

73,
Eric
K8CCA

Another more detailed shot

https://www.radiomarine.org/historic-coast-stations/wlo-mobile

Sorry, if this has been posted before, but there's an interesting photo of Drake gear in a commercial setting in the photo at the bottom of this page:





I remember hearing WLO yrs ago. Looks like they used both 4 line an 7 line equipment

John K5MO

I still have 17 PCBs in stock for this project. Price is $7.00 including postage to North American addresses.
Please contact me off list if you are interested.
--
73, Bernie. VE3FWF
Real?radios glow in the dark

Jim,

Upon closer inspection while not trying to read the schematic while is rotated 90 degrees, I realized that the MN-2000 circuit is not a T configuration.

I do have a couple of questions for you:

-I don’t see why you feel that the MN-2000 circuit is an SPC circuit. It appears to me to be a PI configuration. Both designs do have a tapped capacitor impedance transformer on the output, but the SPC design looks like a T network to me.

-In the video, I am curious why when the frequency is changed with both tuners the Z stays 50 ohms while the SWR goes up. In the SPC tuner case the SWR went up to 1.7 while the Z stayed at 50 ohms. Is Z not the impedance?

--
Bill N0CU

I agree with Bob that the T network can be thought of as two series connected L-networks. Although the L network can do the required impedance transformation in most applications, its main limitation is that, unlike the three component matching networks, it cannot vary the circuit Q. With the L network, the Q is a function of the input and output impedance, so you are stuck with a fixed Q, which in most cases is very low. Although this keeps the losses low, it may be too low to reduce harmonics sufficiently. The Pi and T networks can vary Q in addition to doing the needed impedance transformation, however, the higher Q results in higher loss. I believe that the main reason the T network is rarely used in Ham applications is that it is a high pass function, which does not provide any rejection of harmonics.

?

--
Bill N0CU

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Nope. Its an SPC tuner circuit.

Search for it.

Jim W7RY

This looks like a T network. This configuration?is not as common as the Pi and L. The attached artical is just one of many on the web that discuss how these networks work. It may not be the best article, it was just one I thought looked like it would address your questions.

On Sun, Apr 2, 2023 at 9:32?AM Jim VE7RF <jim.thom@...> wrote:

Both the references sited, are not even close to? the MN-2000.

IF u look at the schematic for the MN-2000, it consist of a PI network, followed by a series variable cap in the output leg to the ant.?

The 1st....' C1 cap' consists of a mess of paralleled? fixed? mica caps, that are progressively switched in by the progressive bandswitch.? ?On 10m, they use 5 x? 68 pf caps in parallel. Reason is, the mica caps don't handle RF current at the upper HF freqs, so 5 are used in parallel.? However, the mica's are stable, and don't drift.? On each lower band, a bigger and bigger mica is added to the grand total..that makes up the 'C1' cap.? ?The coil assy is identical to what's used in the L4B linear amp.? The bandswitch in the MN-2000 is also identical to the bandswitch in the L4B linear.?

The C2 cap in the MN-2000 is a 20-245 pf? air variable. The C3 cap is also a 20-245 pf air variable, but is wired in series with the output..then off to the ant.??

?

Here's?a link to the manual...which includes the schematic at the end.?

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That's because the MN-2000 is an SPC type of tuner. See below. But the MN-2000 uses fixed caps for C1 in this diagram below, as well as C2 shown below, is a split stator type of cap.
The MN-2000, uses two independent caps for C2.

In reality, the MN-2000 is more like the second diagram below. As said before, C1 is the fixed caps that are changed with the band switch coil.
Jim W7RY

Both the references sited, are not even close to? the MN-2000.

IF u look at the schematic for the MN-2000, it consist of a PI network, followed by a series variable cap in the output leg to the ant.?

The 1st....' C1 cap' consists of a mess of paralleled? fixed? mica caps, that are progressively switched in by the progressive bandswitch.? ?On 10m, they use 5 x? 68 pf caps in parallel. Reason is, the mica caps don't handle RF current at the upper HF freqs, so 5 are used in parallel.? However, the mica's are stable, and don't drift.? On each lower band, a bigger and bigger mica is added to the grand total..that makes up the 'C1' cap.? ?The coil assy is identical to what's used in the L4B linear amp.? The bandswitch in the MN-2000 is also identical to the bandswitch in the L4B linear.?

The C2 cap in the MN-2000 is a 20-245 pf? air variable. The C3 cap is also a 20-245 pf air variable, but is wired in series with the output..then off to the ant.??

?

Here's?a link to the manual...which includes the schematic at the end.?

--

Both the references sited, are not even close to? the MN-2000.

IF u look at the schematic for the MN-2000, it consist of a PI network, followed by a series variable cap in the output leg to the ant.?

The 1st....' C1 cap' consists of a mess of paralleled? fixed? mica caps, that are progressively switched in by the progressive bandswitch.? ?On 10m, they use 5 x? 68 pf caps in parallel. Reason is, the mica caps don't handle RF current at the upper HF freqs, so 5 are used in parallel.? However, the mica's are stable, and don't drift.? On each lower band, a bigger and bigger mica is added to the grand total..that makes up the 'C1' cap.? ?The coil assy is identical to what's used in the L4B linear amp.? The bandswitch in the MN-2000 is also identical to the bandswitch in the L4B linear.?

The C2 cap in the MN-2000 is a 20-245 pf? air variable. The C3 cap is also a 20-245 pf air variable, but is wired in series with the output..then off to the ant.??

?

Here's?a link to the manual...which includes the schematic at the end.?

http://www.radiomanual.info/schemi/ACC_matching/Drake_MN-2000_user.pdf

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Hi Gary,

No, I have not done the mod. I would point out though that while looking at the internals the plates may look similar, the 6146 has about twice the plate dissipation of the 6JB6.? The 6146 is about 35 watts and the 6JB6 is 17.5. It is a shame that Drake did not use the 6146 as it could have easily been incorporated at the time. They probably had similar costs. I can remember 6146's selling for $3.50. The mod is not a big deal for someone that has the time and experience. As he pointed out in his article, a lot of the myths like having to recess the tube and that the plate voltage is not high enough are basically bogus. I never liked sweep tubes much but the old 6DQ5 used in early color sets made a good novice transmitter. It has a 24 watt dissipation rating. 6146's in a Drake using the Drake supply would have as much output as the 6JB6's and they would be loafing doing it.? The 6883A is the 12V version and can be found for a cheaper price. For the T4 where the 6JB6's are wired in series, these could be used wired in parallel.
--
Doug, WA3DSP

The two tubes are quite different. The 6146x was designed as an RF power amplifier tube for high duty cycle transmitter service up to 60 MHz, with operational specs described up to 175 Mhz, in various classes of operation (including linear) and signal modes.

The xJB6 tubes were pulse rated tubes designed to be used in low frequency (for us) horizontal deflection circuits. That's all. Sylvania was the only company that bothered to publish specs for RF for their tubes.

The 6146 will take more punishment in ham use than most any sweep tube. The only sweep that has ever impressed me was the late-in-the-game 6MJ6. I once had a pair glowing red when a 10 Meter amp faulted on me and I didn't notice right away. After I let them cool down they were just fine.

If you want to compare pulse ratings, the 6293 variant you mentioned was rated for 3000V plate voltage with 1.5A peak plate current for "Typical operation with rectangular wave shapes" in the recommended test circuit. The JB6 asks for 770V plate with 550 mA peak cathode current.

73

-Jim
NU0C

On Sat, 01 Apr 2023 11:32:13 -0700
"Rick WA6III" <myr748@...> wrote:

6146's are no more rugged than 6JB6's since they have similar plate dissipation.? Remember, sweep tubes in general are rated to operate 24-7 in horizontal sweep osc service with high peak currents and voltages.