logo
Most Viewed Last 7 Days
436MHz DATV Up-Converter (308)
146MHz RD06+RD15 Amp (133)
Archive2 - DATV Transmitter (112)
146MHz RD70HVF1 Amp (105)
Tropo May 2006 (91)
13cm Amplifier (84)

Home



Cluster Activity

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

Solar data:
SFI
74
A-Index
13
K-Index
2
Exp.K
2
Sunspots
22
Activity
qui
GMF
qui
Aurora?
no

My Weather

Date:21/09/17 Time:15:04
Temp:16C
Wind Speed:7.5mph
Wind Dir:180deg
Pressure:1010mB
Humidity:118%
Dew Point:19.6C
UKHASnet
146MHz DATV Tests

Well i got my NoV in October to allow me to use the 146-147MHz band.
Until December i had not made any progress with this until Charles G4GUO released a new program for sending transport streams to the DATV Express, before this it was not too easy to send a low bit rate DVB rate signal but now it is possible.
Charles has also created a modified firmware file for the DATV Express FPGA to adjust filter settings allowing clean output at low symbol rate DVB-S.
https://github.com/G4GUO/express_server

My current TX system:
PVR350 capture card or webcam as the AV source.
ffmpeg re-encodes the video to MPEG4 video then encapsulates in a transport stream.
express_server software is used to setup and send the transport stream to the DATV Express Hardware.
The DATV Express board sends a -10dBm DVB-S signal.
Amplifiers to 1W, down 5dB cable loss to 9el yagi so a few Watts ERP.

Script for re-encoding a PVR's MPEG2 video into lower bit rate MPEG2 or MPEG4 is rb.sh

I am using to two amplification stages comprising of an RD06HVF1 and RD15HVF1 to get from the -10dBm input signal to around 1 Watt level with near enough -60dBc IMD products as per the recommendations.

The amp stages are not pretty but they work fairly well after some tweaking for the best IMD result, initial tests only gave around 200mW clean signal but i found that i had 1nF caps in place of 100pf - wrong value put in parts cabinet... oops!
It shows that we need very high power amplifier devices to generate any real 'clean' power on 146Mhz with the tight spectrum the signal has to fit in unless pre-distortion methods are found...
Charles has come across the SC1894 PA Linearizer chip....

146MHz Amps


146.5MHz Signal 333Ks at 1W




So far the tests have been between Terry G1LPS and myself over a 28km path, Terry has (as of 1/1/15) received a reasonable constellation of the QPSK signal but not fully decoded it using the Tutioune DVB-S software and a Techno trend TT-1600 PCI card.

Terry's Rx setup:
9el Yagi
Mutek LNA > PYE band pass filter > Microwave Modules LNA > Mixer > Line amp > PCI card.
The LO for the mixer is a PA0KLT Si570 VCO kit.

146MHz Close to decoding....



More results to follow soon hopefully!!!!!!!












Last page added:16/08/17 15:45
M0DTS.co.uk