Its good to have even a very inexpensive dummy load for troubleshooting radio
issues. Try googling MFJ when you can/ have some extra $$.
Assuming you don't have one... suggest just making a temp vertical antenna for... say 8mhz, which is abt 29' 3 inches, which you can just put up on halyard
and connect directly to back of rig (try keeping it away from mast/ other conductors as best you can). That length is for exactly 8 MHz, there are many 'antenna length calculation' google
sites for exact freq/ length. If your power indication comes back to normal/ like the other lower frequencies... it might suggest the tuner/ or coax to tuner is not working properly. Don't hold it while testing as it can give you an uncomfortable RF burn. Best to try to keep this test vertical as vertical as you can. Too much sideways run of the wire changes the length calculation.
As far is what's causing you issue, might be:
- tuner not working. Try to get someone to listen for the sounds the tuner makes when tuning on the good bands... when you try to tune it on the higher bands. Should make same sound. All tuners I know make either a clicking sound or a servo motor
sound. No sound... no tuner
- tuner or rig lost
connection to the ground system on the boat
. Check with ohm meter between tuner ground and known boat
ground. If your HF installation
used copper foil for some/ all of the RF ground/ ground runs... be aware that many of us have found our foil completely corroded away in spots from laying against a damp hull/ salt
. You may have to replace. But to get by try just regular wire runs to the ground points/ or if you have a 'floating' RF ground (in addition to your Dynaplate), run the wires as far forward/ aft as you can.
- tuner not getting 12v power. Check its power wire/ fuse/ breaker
on the coax RF connectors or at the antenna connection. Unscrew coax connectors, check center pin AND THE SHIELD connection to the connector. Use ohm meter and also try to twist connector/ shield joint... should not twist.
- if your vertical antenna is in sections, might be corrosion
between the sections. Take apart, wire brush threads, retighten/ seal with tape.
Dyna-plate is covered with marina growth/ someone put bottom paint
on it... reducing its effectiveness.
Back to working on low bands, but not higher ones... the marine SSB
bands and most ham bands are near exact multiples of rack other (2, 4, ...). If the antenna tuner properly turned for 2Mhz... and quit/ failed. The antenna/ tuner setting would still perform pretty well on the next few close bands. But as you multiply the exact 2MHz frequency by 4+ times, the original 'not perfect' tuning position & actual selected 8 MHz frequency can be enough different to cause a bad mismatch and the protective circuitry of the 802 caused the transmitter to several cut back on output power to prevent harm to the rig. Bad grounds on the tuner not only reduced antenna effectiveness drastically, they can allow rf to travel back up to the rig or to the sensitive control wires between the rig and the tuner which will 'trick' the tuner/ rig into making very inaccurate tuner/ rig power settings. Good luck!
(Please let us know what you find. It adds to the body of knowledge we all can use/ learn from. And if you repost for more help, tell us as much detail about what you did/ result, model of tuner would help.)
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