Here is Portsdown-under during my transmission this morning to the Bluff
250mW (measured) into a cheap nasty and slightly modified Ebay Lincho Patch antenna gain unknown (7-10ish?)
The new 500mW PA sports a saw filter that covers the VK 23cm ATV band
How many saw filters can you spot, I think there is room for another one on the second LO that will bring it to 4
Each one cheers the MER up a bit
A MER of 6-8 was recieved at 55km line of sight, so on the boarderline
The 920 webcam produced a surprisingly stable picture throughout the broadcast
Even though the the MER was marginal, the picture hardly pixelated and the sound didn't crack or break
It's not a sports cam and the focus isn't designed for long distance, but great stable encoding
When a car went passed there was a blurred trail behind the image till the GOP caught up
Having ran it for half and hour the batteries were still showing 4 bars
The Portsdown-under was originally designed to show other Hams the low cost way to get started, that's why it's spread out
It uses 2 local oscillators with a base band that up-converts to the output frequency, like a professional modulator
This give plenty of chances for filtering which obviously pays dividends at low power
The saw filters are cheap on Ali-Express and the hardest thing is to relate the part number to the data
You find the 3db points on a saw device are much more generous than the rated band width
They are fiddly to solder but with an art knife and copper tape you can do anything, after the first 20 it gets easier
Sacrificing 3 db insertion lost is a small price to pay for a clean signal
Cheers Roger VK5YYY
QRP DATV
Re: QRP DATV
- portsdown-under
- IMG_0178.jpg (210.04 KiB) Viewed 1842 times
Re: QRP DATV
- 500mW PA with saw filter
- IMG_0180.jpg (167.72 KiB) Viewed 1842 times
Re: QRP DATV
It looks like you have got too much spare time on your hands Roger. Now that winter is over and I have a couple of weeks leave coming up soon i will be heading out of the city for some portable operating. I have been ready for some time but the weekend weather has not been kind.
Wayne
VK5BI
Wayne
VK5BI