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rabbi
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Call Sign : m3kbd/2e0kbd/m0kbd
Posts : 85
Times Thanked : 1
Join date : 2019-07-04
QTH or Location : stockton on tees
Equipment Used : kenwood ts 2000x ascom 70mhz icom vlf/hf/uhf receivers multiband antennas
Age : 62

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PostSubject: rf output power   power - rf output power Icon_minitimeThu Feb 11, 2021 4:45 pm

hi i have a new crt ss6900n multimode 10 meter transceiver i need to reduce the rf output inside the rig as i want it to drive my 4 meter transverter aprox half a watt ssb/fm  thanks for looking stay safe do radio 73s paul m0kbd Very Happy
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Victor
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Victor


Call Sign : 26-CT-3228 Ham M7VIC
Posts : 2535
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Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

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PostSubject: Re: rf output power   power - rf output power Icon_minitimeFri Feb 12, 2021 10:12 am

Hi Paul,

Apart from the external RF power settings there isn't a lot you can do inside the radio that wouldn't require extensive electronic 'surgery'.
There are three service jumpers on the PA stage of the 6900 but these are to disable the PA altogether and two jumpers for setting the biasing to each of the final MOSFETs as they are run in a parallel pair. (Not a push-pull as some suggest!)

You could maybe run a tap from the first PA MOSFET but you would also have to match your impedance with additional circuitry as well as provide an additional low pass filter arrangement. Again, not simple.

The simplest answer is an external attenuator or RF PAD but you'll have to make sure it's more than powerful enough to handle your power dropping requirements. These can be expensive. You could of course build one using a 'Pi' or 'T' resistor networks but you'll need high power resistors that are inductance free such as RF carbon composites and again these we expensive.

There are RF attenuators available on eBay at cheap prices, these are usually a board populated with surface mount resistors. They are low power devices, (<10W), so not much help. I've seen plenty of those 'beauties' with the board burned out!


So sorry mate, not really any simple solutions I can think of. My own HF set has a linear switch and separate RF output for things like external linears or transvertors but it's not something usually found on 'CB' type radios.


All the best,
Victor

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rabbi
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Call Sign : m3kbd/2e0kbd/m0kbd
Posts : 85
Times Thanked : 1
Join date : 2019-07-04
QTH or Location : stockton on tees
Equipment Used : kenwood ts 2000x ascom 70mhz icom vlf/hf/uhf receivers multiband antennas
Age : 62

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PostSubject: crt ss 6900n to use with transverters   power - rf output power Icon_minitimeFri Feb 12, 2021 1:12 pm

Shocked
hi victor thanks for your reply i think maybe selling this radio as it is new with a new extra mic and extra mobile mounting kit i used it once i think i may be able to use a mk 1 lincolin  or some other 10 meter mobile rig with digital frequency read out i have a kenwood ts 2000x but it whould tie up the ts2000x by its cold in stockton on tees 73s paul m0kbd
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Victor
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Call Sign : 26-CT-3228 Ham M7VIC
Posts : 2535
Times Thanked : 174
Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

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PostSubject: Re: rf output power   power - rf output power Icon_minitimeFri Feb 12, 2021 2:39 pm

No worries Paul, I hope you get sorted. Just another headache in the day of life for a radio hobbyist Wink

Keep yourself warm up there!

73s
Victor

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rabbi
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Call Sign : m3kbd/2e0kbd/m0kbd
Posts : 85
Times Thanked : 1
Join date : 2019-07-04
QTH or Location : stockton on tees
Equipment Used : kenwood ts 2000x ascom 70mhz icom vlf/hf/uhf receivers multiband antennas
Age : 62

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PostSubject: Re: rf output power   power - rf output power Icon_minitimeFri Feb 12, 2021 10:11 pm

hi victor i will sell on the crt ss6900n i have aquired a kenwood ts 480 sat the crt puts out 45 watts ssb  nice looking 10 meter set but i will sell it on thanks stay safe do radio 73s paul m0kbd

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