Hf dye china amplifier

[iw2evk]

Hi all
content://media/external/file/8883T
On e bay are sales some mosfet kit for 3_30mhz am fm ssb
It s possible modify for medoum wave band?

Thanks

Roberto

[iw2evk]

https://www.ebay.it/itm/70W-SSB-linear- ... Swyspc7jjy

review HERE https://www.dk9jc.de/blog/equipment/142 ... 17-kx2-kx3

DIY kits 70W SSB linear HF Power Amplifier

●Circuit class AB linear amplifier for SSB AM CW FM power amplifier for low-power radio power connection
●Suitable for FT-817 KX3 other small power stations

Electrical parameters:
1. Power supply voltage: 13.8V
2. Current: 6-10A
3. Maximum input power: 5W
4. Maximum output power: 70W
5. cooled: fan forced cooling
6.Frequency range 3.5--30Mhz (10M - 80M) NEED MODIFICATION FOR 1,8
WARNING: Output prohibit open, short, prohibit VSWR of 2.0 or more
Note:
1.this is kits, not assembled . without heastink
2.Please allow 1-3cm error due to manual measurement. Please make sure you do not mind before you bid.
3.The colors may have different as the difference display, please understand.
Package Included:
1 x 70W SSB linear HF Power Amplifier DIY Kits

[Albert H]

Just for fun, I bought two of these. I omitted the TX / RX switching circuit and the relay. I used a little PWM AM rig that does 1W carrier, 4W peak as a driver, and found that I could get 12W carrier and 50W peak out of this board. I needed a big heatsink, but found that the $4 ones with really thin fins from Banggood (the ones that always need straightening out on arrival!) do the job really well without the need for any blower.

One was lost to the Authorities during a long ~6.3MHz broadcast during the Autumn, but the other has been in regular use from the Venlo area (near to the German border) since then.

If anyone want the circuit of the little PLL-based SW 1W driver, I'll put it up on here. There's nothing special about it except in the way the AM is developed. The next version of the driver will be even simpler, using a standard 4MHz or 10 MHz crystal (get them anywhere without raising suspicions), and another slightly unusual way of developing AM. It's under development at the moment - I'm listening to it relaying a friend's internet station across my workshop as I type this!

[iw2evk]

No modification to perform for use on medium wave band???

[iw2evk]

No modification to perform for use on medium wave band???

[Albert H]

The amp needs a few changes to work down at Medium Wave. I haven't tried it, but it shouldn't be too difficult. I'll have a look and see what I can come up with.

[iw2evk]

Hi Albert,
reading this german document seem possible use this in 160 meter band ( 1,8 Mhz) changing the value of one resistor in circuit (see the part regarding influence of R6 value) http://www.oe1cgs.at/wp-content/uploads ... -HF-PA.pdf

[Albert H]

I've been trying one today at 1 MHz. 0.6W fully modulated is turned into 50W peak at 24V supply. The harmonic content is horrible, so there is significant mismatch in both the input and output circuits. I used a 0.6°C/W heatsink and found that it got pretty warm - also suggesting inefficiency.... This isn't the way to do Medium Wave!

[teckniqs]

Did you try it further up the top of the band around 1.6mhz?

[Albert H]

I tried it on 1440kHz - still useless. At 1.9MHz (the middle of the amateur "top band") it still didn't perform well. 6.4MHz - it was right "on song". 50 Watts out, second harmonic -45dBc before a low pass filter. It really is a shortwave PA!

There are much better ways of doing Medium Wave!