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This is sort of early, but I'd like to use the BITX40 to help more people in our local ARES group get on HF (many of them were VHF-only) -- and in the longer run I think they are going to need a bit more power.? ?I have filters waiting for me at home to try and add another band or two the rig (already ran it at very low power on 80, just enough to reach my WINLINK RMS on the other side of the house) ---? ?

AC2CZ/VE2 's 50-watt dual IRF-510 amplifier caught my eye, particularly because he put in some protection circuitry after lots of experience with the system....and I'm going to try a printed circuit board of his design:

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I'm doing multi-band as well, with modular filters. So far it works great on 80 and 40 (and presumably 60 once I build the filter!) but on 20, output is reduced from 5-7w to about 1w. I'm definitely interested in hearing others experiences. The receiver is definitely not deaf on 20m, as I've used it on 20m after cranking the bias WAY up on the PA (and dealing with the subsequent heat) but it seems like there's some other issue. The IRF510 works fine at 14mhz AFAIK. Input is welcome.



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Ryan Flowers W7RLF

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?<-- Learn how to go digital on the BITX40

No joy tonight. Heard WB2BLJ, N2CQR and W0OIC. No response to my CQ's. At 0347 UTC the interference from 7.275 AM is totally wiping out 7.277 - 20 over S9 on my Kenwood rig. Same transmitter peaking 40 over on 7.275 AM. Hard to compete with 150 KW station - going QRT...73

You might take a look at Bill N2CQR's (he of SolderSmoke fame) rigs. He runs these up at 17m and I think 12m, and their (essentially Bitx) amps have an extra transistor. Pete N6QW ((his chat-partner) has some good explanations too ...

73
Dex, ZL2DEX

Richie,

I have been thinking of this same issue. My BITX40 on 20 meters is slightly deaf on 20 meters. I own an Hendricks BITX20 ( ) which does much better on 20. If you look at the schematics you will find an IF amp using 2 transistors. On the bench this amp seems to put out almost 2 times as much.

Hope this helps

Mike WA3O

Hi John...only heard WB2BLJ calling CQ but no joy yet. Did hear someone else but very fast QSB and couldn't get a call - might end in an "A".

Been calling CQ since 7 EST. Hearing nothing buy noise. Not even broadcast stations!
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John - WA2FZW

Thanks for all
Michale?it's about bfo no vfo.
Vfo is with dds.
the solution would be an extra buffer or the use of dds.
Thanks!
Bogdan,yo3ifx

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I am using this case. It's quite good, especially for the price! It's not a?perfect design but for $8 one can hardly complain.? I have pictures of my build and how I cut the hole for the LCD display on my site:




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Ryan Flowers W7RLF

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?<-- Learn how to go digital on the BITX40

Lots of information on the software defined ham radio group @ yahoo.? I love my W8TEE analyzer and use it all the time around 7mhz. The latest use was checking a LPF for 40 meters. They do like clean power, and lots of it. I can't emphasize this enough. When my batteries get low, it starts doing some crazy stuff. Other than that, it is one of my favorite tools.

Thanks, John, but beyond my bedtime :(

73 de ZL2DEX

Thanks, MIke, but too early. Bugger these timezones! :(

73 de ZL2DEX

I had similar results performing a scan of a 50 ohm dummy load resistor.
The resistor is checked with an other analyzer and VNA and gives no problems with bad SWR even up to UHF.

After some investigations 2 problems are revealed that could influence the bad SWR reading on high bands.

It is best to have bedbug turned on and see what values are measured on the analog ports.

First of all looking at the curve the SWR is not perfect on lower bands too. There probably is a false reading of reverse power because the opamp will not output 0 volts.
(This was the case with my opamp)
When you have this issue, a reading like 4 or so one will see a worse reading on high frequencies.
This is because the signal on low frequencies is much higher than on high frequencies.
If reverse stays the same, and forward voltage drops the line swr will increase on higher frequencies,

The sudden drop Leo sees at 10m I can not explain.

Attached is te picture in the "before situation" I now have a flat line a the bottom using a new opamp MCP602 and boosting the sigal a little.

I still have some issues about design choices made, and the way SWR is calculated.

I for example think this gives the right values.

? ? p = sqrt( ((float)REV) / FWD );?? // Calculate reflection coefficient

??? VSWR = (1 + p) / (1 - p);???????? // Calculate VSWR

I prefer that in stead of this :?

? ? VSWR = ((FWD + REV) / (FWD - REV))

I can not quite figure out why the dds is running on 3V6 and the MMIC is connected to 5V with a 10r resistor where it usually shoud operate on 5v5......?

Do we have a W8TEE K2ZIA Antenna Analyzer group somewhere?

I like this project very much, after some tinkering I have nice very usable readings.

Edwin PE1PWF




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Leuk dat te horen Rob.
I never realized that the spurious burst would also cause this kind of
issues with a PA. So it's good to know that these are now also over!

Happy BitX-ing!
73 Allard PE1NWL

Hello Allard,
Top software update. Spurious Carrier Burst did
make enter my PA many times in seafty mode. Now this is no problem any more!
Thanks!
Rob Bleumer PA0RBL

I think the sale ends tonight.? Shipping times are listed on the page.? You can click the arrow next to the listed shipping method to see other options.? Like most Chinese suppliers sometimes shipping takes twice as long as promised and sometimes it is faster.? I have ordered from Banggood about half a dozen times and find usually things show up toward the longer end of their estimate.

On Sunday nights a few of us in Dubuque Iowa get together on 7277 and try our luck with our QRP rigs. I have 3 BitX rigs and am running 5 watts. I live on a bluff and have a 50' tower with an inverted Vee tuned to 1:1 with a MFJ tuner. We listen on 40 then talk about who we hear on 2 meters through my repeater. We take turns calling the BitX stations and then compare results on 2 meters. I would like to extend to all of you a welcome to use our repeater via any Yaesu WiresX repeater or connection point in your area. My room node is 40870. If you are new to WiresX? you can connect to us by keying in to your local Wires repeater the DTMF code #40870. To disconnect use #99999 Good luck and will be looking for u on 7277. 73's Ed W0OIC