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Re: Gi46b on 2m - Thermal drift problem
For the OP, does that plate block cap even look like a cap at? 144 mhz ??? ?Will it handle the calculated rf current flowing through it at 144 mhz ?? John Lyles,? K5PRO helped myself and Scott out on that 10 kw 6m amp.? ?John used his test gear during a 3 way phone conversation, and was testing various HEC / centralab caps, like the 200 pf? and also? 500 pf variety, in both HT-50/58 size, and also HT-57 sizes.? On some of them, the SRF freq (self res freq)? was as low as just 42-45 mhz.? If 3 x caps were in parallel, SRF rose to 62 mhz.? On the HT-57 caps, in 200 pf size, SRF was 60 mhz...and? even higher, when paralleled.? Above the SRF freq, the cap looks inductive.? ?It's straightforward? test process to find the SRF freq for a given combo of single, or multiple caps in parallel.? |
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Re: Gi46b on 2m - Thermal drift problem -Sorted
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On 3 Jan 2024, at 05:29, Tim Fern <timjfern@...> wrote:
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KW1000 amp renovation, filaments, bias and neutralization.
I recently acquired a British KW1000 linear which uses a pair of 572Bs and is somewhat similar to the SB200. The power transformer was missing but I have been able to fit a replacement from the junk box, it has 2 x 6.3 volt 4 Amp winding with no centre tap so am thinking of connecting the filaments in series. The first problem with this is one tube light up brighter and had 7 volts, the other 5 volts (these were old tubes, one Centron, the other Taylor). When I tried a newer matched pair from Penta the voltages were quite close.
Looking at the schematic for my TL922A I see the CT is connected to the linked filament pins via a 80 uH choke where the drive appears to be applied, although there is also a 0.01 uf capacitor whose purpose is unclear to me, across to one side of the main choke (22 uH). Any advice would be appreciated, also is any bias required in tx and is there a need for neutralization? - am directly grounding the grids. The KW1000 has a few additional turns on the filament choke which goes to a flat plate about 1" square and close to one of the tubes. Mike VK2AMF / G3XEF. Mike Fleetwood Canberra Australia and Sidcup UK. Worldwide email address is: mfleetwood@... |
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Re: Gi46b on 2m - Thermal drift problem
On Wed, Dec 27, 2023 at 11:30 PM, Steve wrote:
the impedance of the original stripline line is no longer maintained because of the additional thickness of that humungously-thick sheet of teflon being used between the two very-thick copper plates, which thickness looks like it has been vastly increased from the original dimensions.I'm not sure if this is in reference to my picture or not, but if so the camera may be playing tricks on you. The teflon I'm using is .4mm thick (in fact it's not even teflon in that mock up, it's a sheet of paper). The copper is only 1.2mm thick (except the bent support bracket, it is slightly over 2mm). Both fall within what was specified in the design I used (which, to be fair, I have no knowledge of its effectiveness... but hey I wanted to try, this is how we learn). Anyways I didn't mean to hijack the thread. Your notes about the dimensions of the cover are appreciated. I plan on making the enclosure soon! Happy new year to all! |
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Re: Tuned input
I see a quantity on Ebay but they are a small fortune. Not what I expected.
On Tuesday, January 2, 2024 at 12:37:28 PM EST, W7WRX <clark@...> wrote:
Mike.? I ordered the board from Fred at FAR.? He did not have relays or the trimmers. I found the relays and have ordered them.?? |
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Re: Tuned input
Arco was the big name in variable caps at one time. Not sure if they are still around. I wonder if there are any articles on that board? I see the original designer has passed. Mike
On Tuesday, January 2, 2024 at 12:37:28 PM EST, W7WRX <clark@...> wrote:
Mike.? I ordered the board from Fred at FAR.? He did not have relays or the trimmers. I found the relays and have ordered them.?? |
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Re: Tuned input
Mike.? I ordered the board from Fred at FAR.? He did not have relays or the trimmers. I found the relays and have ordered them.?? |
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Re: AL-80B fan
You guy's guess was about right! No beer but "fireball"! Bob W4JFA? On Fri, Dec 29, 2023, 8:45 PM Steve <k0xp@...> wrote:
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Re: Tuned input
开云体育
I have tried this in the past. It's a huge KLUDGE and would not recommend it.? That tuner is going to try to tune while you are transmitting, You're constantly showing your radio a bad match every time you change frequency as it has to retune.?
Unless you can somehow make it stop with hard ware or software it never works.??
The old LDG amplifier version had special code that made it work for an amplifier and it had board changes as we only need a small change to work with cathode drive.
Then, The biggest issue, Is the Q is never correct.? The Q is important here for properly function and flywheel effect.? The antenna tuner is never going to match the correct Q.? It's super narrow and will have to retune even with slight changes in frequency.?
If you jump from 14.100 to 14.250 its gonna ratchet away as you try to make a contact OR if its disabled, the SWR on the input will be 6 to 1.
What people end up doing is to remove the AUTO portion and just hard wire the relays for each band.? At that point, Just build a board and tune it.
C
From: [email protected] <[email protected]> on behalf of Brian Moran via groups.io <brian.moran@...>
Sent: Sunday, December 31, 2023 7:17 PM To: [email protected] <[email protected]> Subject: Re: [ham-amplifiers] Tuned input ?
Yes, you would mount the tuner inside your amplifier somewhere; the output of the input network should be close to the tube. Controls for the tuner, and potentially the display, would be on the front panel. ? |
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Re: Tuned input
Yes, you would mount the tuner inside your amplifier somewhere; the output of the input network should be close to the tube. Controls for the tuner, and potentially the display, would be on the front panel. ? |
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Re: Tuned input
开云体育
I guess I don't understand. Your suggesting to install this tuner inside the RF deck?? How will you control it?? How will you switch it to difference bands?How will you prevent it from tuning as you transmit??? on a Grounded grid amplifier, the impedance changes
drastically as you add drive and adjust the output power.? ? On this particular map it could be 1.5 to 3 to 1 depending on drive and tuning.
From: [email protected] <[email protected]> on behalf of Brian Moran via groups.io <brian.moran@...>
Sent: Sunday, December 31, 2023 9:35 AM To: [email protected] <[email protected]> Subject: Re: [ham-amplifiers] Tuned input ?
Here's a late entry to your options: Get one of the ATU kits that are readily available online, running the software from N7DDC.? Modify the HW, and/or the SW. But you have all of the pieces you need in the kits.
software: hardware: just one of MANY available from AMZN:? Or from AliExpress:? I've ordered and built the ATU-100's in the past, they work quite well -- I've used them with QRP radios (e.g. QDX from QRP-labs), as well as a k3 with no tuner.? -Brian N9ADG |
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Re: Tuned input
Here's a late entry to your options: Get one of the ATU kits that are readily available online, running the software from N7DDC.? Modify the HW, and/or the SW. But you have all of the pieces you need in the kits.
software: hardware: just one of MANY available from AMZN:? Or from AliExpress:? I've ordered and built the ATU-100's in the past, they work quite well -- I've used them with QRP radios (e.g. QDX from QRP-labs), as well as a k3 with no tuner.? -Brian N9ADG |
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Re: Tuned input
I really like this option:?
? ?- code is available -? ? ?- parts kits are orderable from a number of sources, including amazon (get it in maybe two days!), aliexpress, etc. search for AT-100. Could be as low as 21.xx from Aliexpress ? ?- testable outside of the amp (put varying loads representing your amplifier input on the output of the ATU100 to see how well they're matched) ? ?- I *think* some models actually show the values of L and C used to match so... you could make a fixed network if you like. Consider the price of the kit a "test instrument" for determining values for your manually switched network. -Brian N9ADG |
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Re: Tuned input
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From: [email protected] <[email protected]> on behalf of mike repinski via groups.io <mikflathead@...>
Sent: Saturday, December 30, 2023 7:52 AM To: [email protected] <[email protected]> Subject: Re: [ham-amplifiers] Tuned input ?
Far circuit boards makes the circuit board for a tuned input. It uses relays and comes in 6 band thru 8 band modules. Check with them. It looks like W4ZT was the designer. Mike
On Saturday, December 30, 2023 at 09:43:40 AM EST, W7WRX <clark@...> wrote:
You don't. They don't make it anymore. They only sell the regular auto tuner.? It's a major kludge. Hence me wanting to install a real tuned input.
C
On Dec 29, 2023 10:33 PM, "Steve via groups.io" <k0xp@...> wrote:
On 12/29/2023 7:45 PM, W7WRX wrote:
Dang... they actually designed it so screwed if you do, screwed if you don't...? 8-/ Actually, that makes sense since these aren't latching relays. So instead, you somehow have to whet it's desire to go retune when the SWR goes too high... how to do that, I wonder? Steve, K0XP
They stopped making that unit years ago.? I tried using the at100 remote ldg.? It decided to tune while I was transmitting. That was it. Smoked.
I suppose the answer to that would be to disconnect power to the tuner after it's done its job.... Or rewire it so it only tunes when power is applied, then you remove power to keep it from self-destructing-under-drive. Yeah, I know: VERY inconvenient! Perhaps that's why they quit making such units. Steve, K0XP --
See my QRZ.com page at |
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Re: Tuned input
Far circuit boards makes the circuit board for a tuned input. It uses relays and comes in 6 band thru 8 band modules. Check with them. It looks like W4ZT was the designer. Mike
On Saturday, December 30, 2023 at 09:43:40 AM EST, W7WRX <clark@...> wrote:
You don't. They don't make it anymore. They only sell the regular auto tuner.? It's a major kludge. Hence me wanting to install a real tuned input.
C
On Dec 29, 2023 10:33 PM, "Steve via groups.io" <k0xp@...> wrote:
On 12/29/2023 7:45 PM, W7WRX wrote:
Dang... they actually designed it so screwed if you do, screwed if you don't...? 8-/ Actually, that makes sense since these aren't latching relays. So instead, you somehow have to whet it's desire to go retune when the SWR goes too high... how to do that, I wonder? Steve, K0XP
They stopped making that unit years ago.? I tried using the at100 remote ldg.? It decided to tune while I was transmitting. That was it. Smoked.
I suppose the answer to that would be to disconnect power to the tuner after it's done its job.... Or rewire it so it only tunes when power is applied, then you remove power to keep it from self-destructing-under-drive. Yeah, I know: VERY inconvenient! Perhaps that's why they quit making such units. Steve, K0XP --
See my QRZ.com page at |
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Re: Tuned input
开云体育You don't. They don't make it anymore. They only sell the regular auto tuner.? It's a major kludge. Hence me wanting to install a real tuned input.
C
On Dec 29, 2023 10:33 PM, "Steve via groups.io" <k0xp@...> wrote:
On 12/29/2023 7:45 PM, W7WRX wrote:
Dang... they actually designed it so screwed if you do, screwed if you don't...? 8-/ Actually, that makes sense since these aren't latching relays. So instead, you somehow have to whet it's desire to go retune when the SWR goes too high... how to do that, I wonder? Steve, K0XP
--
See my QRZ.com page at |
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Re: Tuned input
That's the one. Are they still made?
On Friday, December 29, 2023 at 07:58:57 PM EST, Alek Petkovic via groups.io <vk6apk@...> wrote:
Sorry. I forgot the link.
On 30/12/2023 8:57 am, Alek Petkovic
via groups.io wrote:
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Re: AL80-B tuned input
开云体育I forgot to mention that the capacitor values quoted in the user manual bear no resmblance to the ones mounted on the board. I bought a complete new board from Ameritron and same thing. Completely different to the manual. Alek VK6APK On 30/12/2023 9:43 am, NI5L wrote:
The 2 prior posts are a perfect segue into my question. My input SWR on 30 is over 3 to 1 and 12 meters is about 2 to 1. The rest seem ok.? |
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Re: Tuned input
I wonder if one of these cheap china atu's could be made to work.
They also sell the setup outside if it's box for 40bucks worth a try?? https://www.ebay.co.uk/itm/166521005922?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=Ec92ZeF4TSa&sssrc=4429486&ssuid=z3n9lCyhQEC&var=&widget_ver=artemis&media=SMS In case the link doesn't work, search atu 100 on eBay or similar.? |
Bob