FF9 HF module with only 50% power output :(

[Tadango]

I have a HF module from a FF9 transmitter. It has been checked en adjusted by the robbe technical service and he says it's working good. But it only delivers 50% of its power!! I had more glitches then with other transmitters and the range test is also shorter. He wants me to send it back to have another look. It just cost a lot of money :( I ajusted it myself and can't get any more power out of it so the calibration is ok. How can i modify it to get maximum (normal ;)) power? It is a TW-FM module....

[vintage1]

Could be a low spec gain power device.

depending...

is it pulling the right current?

If not, possibly a replacement power transistor will get it back on spec..

[Tadango]

it draws about 90-100 mAh, that is not enough i guess. 150-200 is normal??

[SlopeKing]

My 9C draws 290mA when on with module, im guessing it may be even less than it should, and my module is dodgy...

[Bruce Abbott]

My 9C draws about 230mA with the TP-FM module installed, and 90mA with it removed. Assuming the rest of the radio draws constant current, the module itself must be drawing about 140mA, which at 9.6V is 1.34 Watts. If the module's power output was 500mW (its rating on 72MHz, not sure what it's meant to be on 40MHz) this would equate to an efficiency of 37%.

I found the current draw varied a bit depending on loading, being only 210mA with the aerial retracted, and 220mA with aerial extended but with the radio on the bench instead of hand-held.

BTW be careful how you measure the current. A cheap digital multimeter I have went completely nuts with the aerial extended, showing a negative readig! I'm fairly sure this does NOT mean that my radio charges its battery while transmitting :rolleyes:

[Tadango]

lol, that should be very nice :)

I have a calibrated meter and it wasn't that cheap ;)

So i guess there is something not working as it should. What type is the power transistor?

[Daniel7866]

My FP-TP-FM module has a 2SC2314 NPN transistor. Some info here http://www.rcgroups.com/forums/showthread.php?t=387442
Just open your module and check ref.
BTW I have this current figure: 80mA w/o module and 220mA with module. Fluke75 as meter.

Daniel

[Tadango]

it looks like the 2SC4272 (SMD is very hard (eeh not) to identify)

I just try it :) If i can get one :(

[Nick Reffold]

Hi Tadango

I had a friend in the UK had a similar problem. You might want to think about checking the frequency and bandwidth of Tx with your Rx. Did the Robbe tec check your receiver? Is it a Futaba rx - some other makes have much more narrow bandwidth.

Nick

[Tadango]

It is a futaba rx but i also had problems with yeti, schulze and graupner ;) The receiver is not the problem, my fx 18 works perfectly with all receivers. I use the same crystal in both transmitters. The power output is also 200% compared to the ff-9 ;)

[Tadango]

i found the problem :) A capasitor had a broken contact which made it unstable. I replaced it, re adjusted the whole thing and it works perfect now :)

[Daniel7866]

i found the problem :) A capasitor had a broken contact which made it unstable. I replaced it, re adjusted the whole thing and it works perfect now :)

Great!

How did you find it? Schematic?
What is your current drain now?

Daniel

[Tadango]

current drain is hard to measure. Range check is great. I have less glitches (none until now :)) with a simple jeti rex5 receiver. I adujsted the modulation signal so it is a bit louder. I does not have any effect on nearby channels zo i don't really care about figures right now ;) i will measure the current when i have a better methode.

I found the broken capasitor when it would not start and I check all capasitors by shunting them with another one. 1 did respond and the capasitor fell apart when i wanted to desolder it. I compared it with my FX18 and the resonate part is 100% identical. The whole HF part is almost the same except for 1 extra filter on the FX18.

[FredericG]

robbe technical service and he says it's working good. But it only delivers 50% of its power!!
Please forgive my ignorance, but how did you know it did not deliver the right power; how is it measured?

Thanks,
Frederic

[Tadango]

There where a lot of glitches and the range test was not good. I made a simple SWR meter and it measured almost the same value on other transmitters but about 50% on mine. Range test was also about 60% of a normal set.

This al adds up to 1 conclusion, nog enough power ;) Maybe more or less then 50% but it is an indication. Power measures the same now :)

In some situations it looked like it had 100% but changing something made it drop to 50% again. It just was not stable. No matter what i do now, it stays good :)

[SlopeKing]

Reckon you could post a thread on building that equipment, I would like to diagnose my radio...

[Tadango]

No problem :) You need 2 standard diodes, 1 capasitor 10uF and a home made coil with an inner width of 30mm and about 300mm length. Also needed is a small meter with mAmp range (digital cheap multimeter will do :))

connect it like in the picture :)

[yctseng]

I think the DIP meter is beter. By the way, the diodes should use 1N34 or 1N60. Not
1N4148 !

Here is the DIP meter link if you want to DIY....
http://yb0ah.tripod.com/homebrew/project/test_eq/dip_meter/dip.html


http://www.universal-radio.com/catalog/meters/1758.jpg

[FredericG]

If I am not mistaken, this measures the signal strength. In addition, one needs to know if the emitted frequency is not a bit of. How is this measured, using a spectrum analyzer?

Frederic

[Tadango]

i just tuned it to maximium output power (best resonance for the crystal ;)) and did some range tests checking the influence of the different settings. Is seemed that the highest output power in every stage was the longest range....

[PLMS]

No problem :) You need 2 standard diodes, 1 capasitor 10uF and a home made coil with an inner width of 30mm and about 300mm length. Also needed is a small meter with mAmp range (digital cheap multimeter will do :))

connect it like in the picture :)


Hi, sounds interesting.
How many turns of wire on the 30mm roll (a paper sandwhich wrap roll ?) did you use ?

Also, would a small load resistor be needed to discharge the cap ? 470K etc.

MS

[vintage1]

Hi, sounds interesting.
How many turns of wire on the 30mm roll (a paper sandwhich wrap roll ?) did you use ?

Also, would a small load resistor be needed to discharge the cap ? 470K etc.

MS

Nope. The meter does that.

[Tadango]

no, since u use the A function of the meter is already had a very low resistance ;)

i have made a coil with 1cm spacings between each wind. so 30 suold be possible on a 30cm rol :) I made the rol of simple A4 roled around a tube. The wire is taped to the paper and holds verything together.

[PLMS]

Thanks
I missed the info about using the mA mode of the meter. I assumed you meant to use the mV side, which has many Mohm on my Fluke DVM. I'll try this out.

BTW, do you see much difference in whether you have the tip section or base section of the TX antenna in the jig ?

Martin

[arneansper]

Regarding the SWR meter: can it be used to compare the effectivness of the different antennaes? I bought a Becker antenna for my FX-18 and would like to compare it to the original.

Arne

[Tadango]

There is a lot of difference in power changing the distance from the antenna to the coil and the direction. You have to make a test setup so that the lengt en location and direction of the antenna is the same, every time. It can be used best for comparing transmitters and antenna's ;) Also the tip and base power readings are different. The best thing to test is the tip compared with the shorter antenna at a distance of about 15cm.

[PLMS]

Hey Tadango

FYI, I built your coil and did some testing with it, while also tuning some Futaba modules.

The main thread is here
http://www.rcgroups.com/forums/showthread.php?t=430241#post4490778
Martin

[pegase]

Hey Tadango,

I have the same problem with a FX18 TX (half power current).
Do you have some schematic of the FX18 ou robbe HF module to help me ?

Thanks

Pegase