Whats on your Workbench ?
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Whats on your Workbench ?
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23-01-2022, 08:16 AM
Great work Tim, very impressive figures.
If possible, would you be able to document the process and what parts you used where? This would be quite attractive to many, I'm guessing. Regards Jayson
23-01-2022, 08:19 AM
(23-01-2022, 08:16 AM)VK1JA Wrote: Great work Tim, very impressive figures. Absolutely! - this is the intent. I'll either make some sort of web site or create a document pdf thing to share or both  cheers Tim
10-02-2022, 03:13 PM
Hi all,
After playing around with baluns, caps and such I declare the build of the Chinese 2m amp pallet done! I now have temperature compensation in the bias circuit and tuned it for best performance and efficiency, it now produces 57.6dBm out aka 575w for 4w in at an efficiency of 76%. 2nd harmonic is at -58dBm others way below that. Now that I am happy with it I need to build it into a box wit associated protection and PTT circuits to make it useful. Also have to write all this up for others to follow cheers Tim
15-02-2022, 02:35 PM
While I wait for bits to box up the 2m amp to make it useful I'm proceeding with my "QRO Project" which is to build amps for 2m,70cm and 23cm.
Next pallet on test is a build for 1296 based on W6PQL parts. 1st test of my 1296 amp pallet producing 500W+ out at 1296.1 cheers Tim
16-02-2022, 09:53 AM
Looks Good Tim.
Ive been playing with the Russian version which is two boards but getting similar results after some small mods. The filter is way over kill for the 500w MRF300 amp but it works. Be interested to see what you changed and how it stacks up with what I did. Not quite getting the same power out, 530w with 4.5w drive at 74%, so maybe more experimentation needed! Cheers Roger ZL3RC
17-02-2022, 01:59 PM
Been keeping an eye on this, be interested to see the final result.
In the meantime, have dusted my workbench off and removed most of the spiders - currently working on a replacement AD9850 based VFO module for the FT101Z's in conjunction with a UK ham. Designed to be (hopefully) a straight drop-in under the original VFO shield apart from a mounting bracket and coupling to the encoder. Nearly there on the schematic and software front - about to test the software this afternoon. There may be another version using the cheaper AD9833 module once this one is finished.
02-04-2022, 02:03 PM
Keeping on with my QRO project for 2,70 & 1296 I decided I wanted some nice switches for the front of my amps when I box them up. Jaycar et al. want north of $10 per switch for unlabeled.
Found a mob on Aliexpress... https://www.aliexpress.com/store/4352002 that will custom label a switch with text or a graphic see pic. Also cost less than the local mob. cheers Tim
03-04-2022, 08:42 AM
Nice find with the switches! Did you do the labeling yourself, or can you order them with custom lables?
03-04-2022, 05:18 PM
(03-04-2022, 08:42 AM)VK1JA Wrote: Nice find with the switches! Did you do the labeling yourself, or can you order them with custom lables? The DianQi store customize the switches for you. You select the custom option in their web store and then either state what text you want on the button or provide a GIF of the graphic you want. You do that in the message channel on their store front. cheers Tim
02-06-2022, 07:27 AM
Hi all,
I thought I'd post a quick summary of the changes to the Chinese 2m amp board I built... My white coax measured as 25 ohms, lengths worked out to 4 inches Blue output coax also got quite warm, replaced that with 6 inches of RG400 Input match is completely wrong, you need to use 3 turns instead of 4 turns on the input transformer. Also all those series caps don't help either. Replaced those with 16pF ATC100b for better match (11pf+5pf in parallel). It doesn't need to be an ATC but I had spare. The wire supplied for the LPF is 1.2mm and a tad thin for this amp. They get quite hot so I rewound those coils with 2.5mm wire to better handle the current. The 100pF parallel caps on the output are not optimal. Replaced with 2x30pF caps in parallel in each leg. Also added a 10pF cap between drains which increased gain and efficiency, actually, its not directly across the drains, its at the input of RG400 - see photos. Added temperature compensation to the bias circuit be installing a 10kNTC in series with an 80k resistor and putting that in parallel with the 10k resistor in the bias voltage divider. End result 575W out for 4W in. 15.1A@50v so about 76% efficient at 144.200 MHz High resolution photos of my build can be found here... https://photos.app.goo.gl/xgV5319t5iQ9F4iV9 cheers Tim |
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