logo
Most Viewed Last 7 Days
GB3YT (YV,YX) (329)
EME In 2006 (328)
Chirp Sounders (328)
Microsource YIG Synth (328)
11km on 134GHz (328)
13cm 200mW Comtech info (328)

ALL


Cluster Activity

Spots per uW band today:
UK spotter or spotted only.

Solar data:
SFI
70
A-Index
3
K-Index
1
Exp.K
0
Sunspots
0
Activity
qui
GMF
qui
Aurora?
no

My Weather

Date:01/01/70 Time:00:00
Temp:C
Wind Speed:0mph
Wind Dir:deg
Pressure:0mB
Humidity:%
Dew Point:-20C
UKHASnet

Recently i built another 2m Amplifier using the RD70HVF1, it is relatively cheap at under 20 GBP each but only available on ebay form far east!
I ordered two for 36 GBP, ebay item 191149037109.

This device is rated at 70W CW so was a good candidate for getting more 'clean' power on 146MHz Digital ATV.

Initial tests show very good results at up to 5W output, -55dB IMD3. I can get about -58dB with some tweaking but not very repeatable!, using the amplitude only pre-distortion in the DATV Express i can manage 6W at -60dB IMD3.

The design is extremely close to the RD06 and RD15 devices but with a couple of value changes in L/C.

I have used trimmers for a few caps during testing but the values which i found to do the job are shown below.
I have very little knowledge on amplifier design, i just twiddled a bit until i got what i needed, i'm sure someone else could do a better job!

The device is biased up well so you do need to get the heat away from the device well, i used a copper spreader to move the heat and it works very well, a fan is a must on 5"x4"x1" heatsink!

I think the best way to drive this amp is using an RD06 device which has very clean output at 50mW level, you then need ~1mW drive from the modulator.

Here is an updated schematic and photo: (fixed cap values added 18/9/15)

RD70HVF1 Amp V3



RD70HVF1 Amp Photo



RD70HVF1 Spectrum 5W
















Last page added:25/03/00 18:32
M0DTS.co.uk