The cheapest I could find a MAR-3 with shipping cost is 12 USD.... I guess buying a finished UHF amplifier will be cheaper.

 

The cheapest I could find a MAR-3 with shipping cost is 12 USD.... I guess buying a finished UHF amplifier will be cheaper.

Yes, and it will actually work!
I'm happy to see you arrived at post #4. Going through the, "why" of it is good for learning, so I can't fault you on that.

 

I tested some comercial uhf tv preamps, they usually have low gain, because of the poor overload charistics of tv sets. I got a kit of mmic's direct from minicircuits labs a while ago, and thoes things are practicly bullet proof. I have used them for preamps for teswt equipment and radios, as well as for a little more gain in radios also.

 

Hello,

In europe they are much cheaper:
http://www.box73.de/product_info.php?products_id=724
Here is the complete table with MMIC's available at that company:



That site has EUR 5.90 as international shipping rate:
http://www.box73.de/shop_content.php?coID=14

When you expect strong signals, you could have a look at the ERA5 or ERA6, wich do have a much higher IP3 point.

Bertus

 

I'll bet Mr. Scott could do it Captain.
Or maybe Checkov...
Keep trying, it could be something waiting to be discovered.

Good luck

 

I tried already with a BC547 and a N2222 NPN transistor, but I think they cannot handle the frequency. I didn't see any improvement in the signal strength. Perhaps this would only work for analog tv channels and not digital tv?

With those transistors - NO CHANCE!!!

A good source of UHF transistors is the tuner from a scrap TV, although many these days use dual-gate MOSFETs - and you'd need to find a pretty old TV to get through hole components.

If you can get very fast industrial transistors that are nearly fast enough but not quite - the grounded base configuration might help, they don't give any current gain, but they provide modest power gain and a lot of voltage gain. They also have lower input impedance that's easier to match to aerial feeds.

In the valve era the low gain at high frequency problem was alleviated by the casc-o-de amplifier - a common cathode stage directly driving a common grid stage.