Post subject: Mod to antenna tuner Could it still handle 100 watts
Posted: May Fri 26, 2023 1:17 am
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Joined: Jan Sat 18, 2020 3:37 pm Posts: 80
Location: Daytona Beach FL
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I added a DPDT switch for bypass/center off/tune positions, rated 5A 125VAC. All wires are the same solid gauge wire that the MFJ-901B originally had (only NOW they're directed through the toggle for various functions). No problems with 5 watts QRP, how high could I safely push this, power-wise?
Post subject: Re: Mod to antenna tuner Could it still handle 100 watts
Posted: May Fri 26, 2023 9:03 am
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Joined: Jan Sat 18, 2020 3:37 pm Posts: 80
Location: Daytona Beach FL
The '901B (in its original design, same var. caps) is rated 200 watts RF. I might be reinstalling a 9:1 unun outside (like I had before), lessening any degree of mismatch (although they are correct, such a marginal multiband antenna IS more prone to noise, sometimes)
Post subject: Re: Mod to antenna tuner Could it still handle 100 watts
Posted: May Tue 30, 2023 11:03 pm
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Joined: Jun Mon 20, 2011 5:09 pm Posts: 1318
Location: N St Cloud, Mn
I don't know that the 9:1 transformer is going to do much in very high SWR conditions. You should include a DPDT switch in order to reverse the connections so you also can check for 1:9 conditions.
I built a 6:1 to 1:6 5PST with DPDT switch. I have two wire antennas and do not use a tuner as the antennas are always close to resonance.
_________________ Prediction is difficult, especially about the future. Niels Bohr
Post subject: Re: Mod to antenna tuner Could it still handle 100 watts
Posted: May Wed 31, 2023 1:21 pm
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Joined: Jan Sat 18, 2020 3:37 pm Posts: 80
Location: Daytona Beach FL
...the 9:1 unun is waaay out there feeding the base of a 50-60' wire (or one of those lengths recommended for the antenna). Even WITHOUT the transmatch, the swr is usually quite low for most bands (I just like to use the transmatch to flatten swr for any remaining bit), transmitters kinda like that.
