07-02-2022, 04:45 PM
Mike
I finally located the datasheet on the FRM10N-1A1 relay (see PNG images below), and while it is rated at 12A for 50/60Hz, the RF capability is probably far lower. Interestingly the relays in your photo date to 2007 despite (I guess) that the tuner would be of more recent manufacture (???)
Your image #2 is telling : the longtitudinal damage line means that the contact connections and/or contacts themselves have an extremely large current flow through them thus the isolated heating points. That current must be circulating RF current (rather than DC) at a very high magnitude to generate the heat within the relay structure.
Image #1 simply shows mass destruction.
I found a poor-quality image of the schematic of the SGC-235 in a user manual PDF but somehow I have doubts as to its accuracy : it shows 4 x 4.0uH inductors in series with relay contact sets across each inductor YET there is only one relay coil/power switching feed. That would mean it simply switches 16uH of inductance in-line to the output terminal. I can understand putting in 0uH, 4uH, 8uH, 12uH and finally 16uH to cope with different frequencies to obtain impedance matches but just either 0uH or 16uH does not make design sense.
The TS480HX has no internal tuner according to what I saw, presumably to a low-impedance/50 ohm port. Then you have the SGC-235 in line to a high impedance connection to your 'longwire'. Can I make a suggestion : insert a UN-UN at the output of the SGC-235, probably a 4:1 ratio or so. The idea there is to transform the impedances reflected by the antenna at the various frequencies into a lower impedance ratio for the SGC-235 to tune into, thus it will set up it's internal LC matching values differently, maybe avoiding the high RF current condition.
Personally I use LDG autotuners but they are rated at about 100W (reliably) and I use one at a known 100W-state on FT8 on HF while portable and it continues to be reliable. I know you can use LDG tuners on Icom, Yaesu & Kenwood transceivers but don't know if they will handle the 200W near-continuous RF power of your TS480HX. One of thuse plus an UN-UN might be an alternative - although it does not fix your current problem.
Anyway, a different thought line might trigger something that is a solution for you.
73 Doug
I finally located the datasheet on the FRM10N-1A1 relay (see PNG images below), and while it is rated at 12A for 50/60Hz, the RF capability is probably far lower. Interestingly the relays in your photo date to 2007 despite (I guess) that the tuner would be of more recent manufacture (???)
Your image #2 is telling : the longtitudinal damage line means that the contact connections and/or contacts themselves have an extremely large current flow through them thus the isolated heating points. That current must be circulating RF current (rather than DC) at a very high magnitude to generate the heat within the relay structure.
Image #1 simply shows mass destruction.
I found a poor-quality image of the schematic of the SGC-235 in a user manual PDF but somehow I have doubts as to its accuracy : it shows 4 x 4.0uH inductors in series with relay contact sets across each inductor YET there is only one relay coil/power switching feed. That would mean it simply switches 16uH of inductance in-line to the output terminal. I can understand putting in 0uH, 4uH, 8uH, 12uH and finally 16uH to cope with different frequencies to obtain impedance matches but just either 0uH or 16uH does not make design sense.
The TS480HX has no internal tuner according to what I saw, presumably to a low-impedance/50 ohm port. Then you have the SGC-235 in line to a high impedance connection to your 'longwire'. Can I make a suggestion : insert a UN-UN at the output of the SGC-235, probably a 4:1 ratio or so. The idea there is to transform the impedances reflected by the antenna at the various frequencies into a lower impedance ratio for the SGC-235 to tune into, thus it will set up it's internal LC matching values differently, maybe avoiding the high RF current condition.
Personally I use LDG autotuners but they are rated at about 100W (reliably) and I use one at a known 100W-state on FT8 on HF while portable and it continues to be reliable. I know you can use LDG tuners on Icom, Yaesu & Kenwood transceivers but don't know if they will handle the 200W near-continuous RF power of your TS480HX. One of thuse plus an UN-UN might be an alternative - although it does not fix your current problem.
Anyway, a different thought line might trigger something that is a solution for you.
73 Doug
Doug VK4ADC @ QG62LG51
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.