Would it be possible to boost the signal from an aerial antenna with a simple class A amplifier circuit to get a stronger digital tv reception?

With something similar to this:

 

I don't see much hope for that circuit being useful, since it contains no meaningful details. What frequency band(s) do you think are occupied by digital television channels?

 

I don't see much hope for that circuit being useful, since it contains no meaningful details. What frequency band(s) do you think are occupied by digital television channels?

I believe around 600 Mhz

 

Antenna amps are very inexpensive. Why build one?

 

Antenna amps are very inexpensive. Why build one?

It's more fun

 

OK. You are risking about $2 worth of parts. Build it and tell us how it turned out.

 

OK. You are risking about $2 worth of parts. Build it and tell us how it turned out.

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?

 

It may be fun but building even a 600 MHz pre amplifier is a pretty good technical challenge, right down to not just the components but how the board is constructed and components spaced. This is likely why even experienced RF engineers more often choose to buy over build. Next the antenna and feed line are everything too. High end RG6 (75 Ohm) coax is preferred with a good high quality high gain antenna on a good rotor system. There is much more to this than the simple common transistor amplifier you posted.

Ron

 

It may be fun but building even a 600 MHz pre amplifier is a pretty good technical challenge, right down to not just the components but how the board is constructed and components spaced. This is likely why even experienced RF engineers more often choose to buy over build. Next the antenna and feed line are everything too. High end RG6 (75 Ohm) coax is preferred with a good high quality high gain antenna on a good rotor system. There is much more to this than the simple common transistor amplifier you posted.

Ron

I understand, but my thought was that a class A is a broadband amplifier and perhaps with the right transistor it could actually work.

 

Well I certainly agree you have nothing to lose by trying. During my formative years, long, long ago I did discover that even a blind squirrel finds an occasional acorn. Additionally you should come away having learned a few things so by all means continue to march.

Ron

 

I want to clarify that this device I try to build goes between the coaxial antenna cable and the tv antenna in-plug. It's not an RF circuit, so it shouldn't be too complicated nor require special metal housing, etc. Please correct me if I'm wrong. As far as I have learned, a class a amplifier does not change the frequency. It only boosts the signal amplitude.

 

I want to clarify that this device I try to build goes between the coaxial antenna cable and the tv antenna in-plug. It's not an RF circuit,

Absolutely wrong.
This is like saying, "If I scrape the flash powder out of my firecrackers, will it make my SR-71 spy plane go faster".

 

Absolutely wrong.
This is like saying, "If I scrape the flash powder out of my firecrackers, will it make my SR-71 spy plane go faster".

What I meant to say its not a sophisticated receiver / transmitter RF circuit. Just a transistor boosting the current.

 

I'd be surprised if you get any signal at all through such a device made from general purpose transistors. It just doesn't work the way you think.

 

I seem to be on to something. After some research I found this http://www.talkingelectronics.com/projects/200TrCcts/101-200TrCcts.html#69

VHF AERIAL AMPLIFIER
This amplifier circuit can be used to amplify VHF television signals. The gain is between 5dB and 28dB. 300ohm twin feeder can be used for the In/Out leads.

This looks a lot like a class a amplifier.

 

VHF television signals can mean 54-88 MHz., which is a far cry from 600 MHz.
I can't find any evidence that you can buy one.
Wait, I see it on a list. Still can't find a datasheet.
Found it:
http://www.onsemi.com/pub_link/Collateral/MPS918-D.PDF
Typical GainBandwidth Product is 600 MHz. which means you can get a gain of 1 at 600 MHz. The max is 1500 MHz. So if you buy a bin full you might get one that will give you some gain of 2 or 3 at those frequencies. Pretty tough to make it work there. Certainly those capacitor values will be too big.
BTW do you have any test equipment to let you know it is working?

 

Somebody just mentioned to me that digital tv is now UHF and not VHF and requires microwave technology. He seems to be savy as he said he built a VHF antenna amplifier circuit before.

 

The transistor in the datasheet matches the 2N3563 in the circuit diagram I posted. It looks like this one can handle the required Mhz for digital tv. The BF198 only seems to handle 400 Mhz. The BC547 I tried can only do 300 Mhz. I suppose if I use a 2N3563 the signal should be at least equal or slightly boosted.

If a BC547 can do 300Mhz, wouldn't it also work in the VHF amp circuit I posted?

 

As mentioned, you just can't cobble together a UHF preamp with RF building experience. Best bet is to buy a UHF preamp. Channel Master makes some pretty good ones.

I don't use a preamp as nothing beats a good UHF antenna mounted and pointed properly. Try www.tvfool.com to see what you can expect to get on OTA from your location.

 

This circuit right here looks like a very promising UHF antenna amplifier and it's also Class A type http://www.electroschematics.com/447/uhf-antenna-amplifier/

I just don't think I have the experience yet to fabricate L1 to L4

I just checked out the 2SC3358, it has a GainBandwidth Product of 7 GHz !!!! Crazy, prob hard to get http://pdf1.alldatasheet.com/datasheet-pdf/view/117939/UTC/2SC3358.html