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Discussion Starter #1 (Edited)
A new Item saw on ebay search, a laptop UHF amplified antenna, Im guessing the antenna is a folded dipole, but the 6v amp may have some mobile uses to it, have not seen an amp for portable use before like this one I know this is not the forum for selling, though I was wondering if the amp is something worth salvaging?


Clip mechanism for Laptop PC and poratble DTV
low noise amplifier technology(<2dB)
Support USB powering
13+-5db gain(Built-in Amplifier)
VHF-h and UHF reception
attached Cable (100cm) with power inserter

Specification:
Frequency range : 174~870MHz
Gain: 13+-5dB
Noise Figure : <2dB
RF Output Impedance 75 Ohm
RF output cable : 1.5C~2V/Male/USB Jack/100cm with Power Inserter
Dimension : 237 X 28 X 13.5mm



main image here _> http://i148.photobucket.com/albums/s18/estefan2020/laptopuhf.jpg aditional image here ->http://i148.photobucket.com/albums/s18/estefan2020/laptopuhf4.jpg
 

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though I was wondering if the amp is something worth salvaging?
If the noise figure is accurate, it looks pretty good. Its usb powered, so it would be a 5 volt DC preamp.
 

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Found a few for tv's on ebay for $30-40
What did you search on ? I couldnt find any for that price range.

Remember, you want input from 50 - 698 mhz, ATSC (not DVB-T)

Or at least 174mhz to 698mhz ATSC.
 

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I found two of those, actually, but I'm not linking the item due to the manufacturer. Search for "ATSC meter", I got two hits this morning. (Or you can look up the item number 290526892966)
 

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Well By the looks it may be a simple folded antenna, but thats fairly predictable, what is interesting is the amplifier inside. I have only seen a hand full of UHF amplifiers that can run off of 12volts, and not many at all that can run on 5v. The noise looks quite low, and may be of interest to others, for projects.

I remember some years back, radio shack had a mini vhf rabbit ear amplifier using 2 AA batteries, for its hand held tv's, but could not find any of them anymore. This amplifier could be placed under the bi-quad antenna on page 1 in this thread, powered by 3 or 4 AA's if the situation warranted it, I really not sure what to expect from it, though will be ordering one, and taking a look inside.

So, from the original concept of a "Mobil pick up an go" antenna, that is suited for a picknic/table/car top/ other, that can, have a built in, antenna orientation assistance, and possibly an amplifier for boosting if necessary.
 

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Im surprised they havent come out with commercial solar/battery powered ones. Preamps are usually one transistor low power devices. The clean DC power provided by a battery should help lower the noise.
 

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Discussion Starter #8
Well I am guessing, the demand for VHF amps for portables, have not hit, due to the recent transfer to digital tv, and the price of portables is still a bit on the high side. I was quite lucky, to find at Christmas a thrift store selling last years model unopened 7inch digital tv 2 hr battery for $39. The sticker price was for $149. I really don't see the portable market exploding for a while. portable analog tv's was sold at $35, add your 8 C batteries to it.

Due to the nature of digital vs analog, you were able to get a crappy picture with so little signal. Now with all or nothing digital, and the fact you need about 70% or more of the signal to actually have a channel come in consistently, I don't think the portable UHF amp market really seen the light of day. When the digital tv's get under the $40-50 mark I think there may be a slight market.

I remember 20 years ago there was "rainbow kit" I think that had a single 4 terminal surface mount transistor for 10db tv gain. low parts. Will have to look though my junk to see if I still have the schematics, thanks for helping me remember that. Though at that time, they were not talking about noise.
 

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ATSC-M/H (Mobile/Handheld) is much more robust, esp. when your roof-top antenna blows away....
Broadcasting ATSC-M/H in the U.S. is already active in many cities...but none in Canada...so far:
http://www.rabbitears.info/market.php?request=atscmph [66 Stations Reporting]
http://www.openmobilevideo.com/media-relations/press-releases/ [Click on the Map]
Maybe we'll see a lot more Mobile DTV's with ATSC-M/H come out this year to put away in our survival lockers....

There might be a later list of ATSC-M/H compatible (ATSC A/153) USB Stick Tuners (et. al) other than:
http://www.tvtechnology.com/article/107108http://www.tvtechnology.com/article/107108
http://www.mobile-dtv-viewer.com/tunerlist-atsc.html
http://www.mobile-dtv-viewer.com/

PS: What sort of services are envisioned for ATSC-M/H:
http://www.omvc.org/_assets/docs/broadcasters/mobile-dtv.pdf
 

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I think the build yourself I posted with a 6 position switch, and a few preset filters for channels of your choosing could be a lower cost approach, then spending a few hundred dollars on a nice digital one.
 

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I think the build yourself I posted with a 6 position switch, and a few preset filters for channels of your choosing could be a lower cost approach, then spending a few hundred dollars on a nice digital one.
The problem with build it yourself models is the critical rf alignment of all the coils and parts at those frequencies. To align them properly, you need even more expensive equipment, heh.
 

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Discussion Starter #12
Well If anyone is interested with the above antenna, antenna amplifier, Here are a few photographs

http://i148.photobucket.com/albums/s18/estefan2020/antenna1.jpg
http://i148.photobucket.com/albums/s18/estefan2020/antenna2.jpg
http://i148.photobucket.com/albums/s18/estefan2020/antenna3.jpg
http://i148.photobucket.com/albums/s18/estefan2020/antenna4.jpg
http://i148.photobucket.com/albums/s18/estefan2020/antenna5.jpg

All sm components on a 1 sided board, U1 sb0359g with 4 soldering points.

The sb0395g is not listed in mouser digikey, or jameco from their search. I am wondering if anyone will have more luck identifying this chip I would really like to know the max/min operating voltage and the frequency rage.

I did test this unit out on a 7inch Mobil tv, connected the power to a computers usb port by my window. The tv was able to lock on to a station when the antenna was turned to a specific direction, barely, My location is not ideal for ota reception, but with the omni stick that came with the tv, with the same station there was no lock on a signal at all.

Operating on 2 or 3 batteries would be an ideal. Replacing the built in antenna with a bi-quad, and having a switch change antenna input to the amp, and powering the amp would be a nice design for a mobil pickup and go design antenna.
 

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Nice pictures, thanks. :p
First, the section in the middle looks to be just an internal pcb balun.

Second, the antenna itself looks to be a cross between a solid bowtie and solid folded dipole. My guess is a Raw Gain of between 3 and 4 dBi. 5 dBi tops.
Interesting design pattern, will have to model a wire version of it in the future.

I have done models of a saw toothed type bowtie, and there was no basic difference between it and a normal bowtie, from what I found.

I did test this unit out on a 7inch Mobil tv, connected the power to a computers usb port by my window. The tv was able to lock on to a station when the antenna was turned to a specific direction, barely, My location is not ideal for ota reception, but with the omni stick that came with the tv, with the same station there was no lock on a signal at all.
That kind of says nothing, except that rubber ducky TV antennas have high negative gain. Whats the NM of that channel at your location per TVFool ?

Measuring apples to apples, I would definately like to see a shoot out between the common TV rubber ducky antennas VS a large paper clip, heh.
 

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Operating on 2 or 3 batteries would be an ideal. Replacing the built in antenna with a bi-quad, and having a switch change antenna input to the amp, and powering the amp would be a nice design for a mobil pickup and go design antenna.
Well, depends on the batteries of course, heh. Two AAs is only 3 volts, 2.4 volts if rechargeable. Three would be 4.5 volts, still below the 5 volts from the usb port. 4 would be 6 volts, which should still be OK, unless the engineers designed too closely. 4 of the rechargeable would be 4.8 volts. On a portable preamp device, I would probably go with overvolting (ie overclocking) to the 6 volt level. Of course, lead acid 6 volts single packaged batteries can be had cheaply.
 

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Discussion Starter #15
Well, depends on the batteries of course, heh. Two AAs is only 3 volts, 2.4 volts if rechargeable. Three would be 4.5 volts, still below the 5 volts from the usb port. 4 would be 6 volts, which should still be OK, unless the engineers designed too closely. 4 of the rechargeable would be 4.8 volts. On a portable preamp device, I would probably go with overvolting (ie overclocking) to the 6 volt level. Of course, lead acid 6 volts single packaged batteries can be had cheaply.
well I hope its a pcb balun, otherwise it was designed without one.. lol.

By the dc in pads there is a "D2" diode? marking and the big black chip is marked with 3 Vertical lines and "M3" possibly anticipated 6volts.

then again a 3dc to dc5v converter would be overkill, or a few diodes as a voltage drop.

Still surprised that there is no shielding around the components, especially if it was designed to be placed on top of a laptop screen, the harmonics and/or noise from the laptop itself may be amplified into the input, even though its not the same frequency for tv, would have though some piece of square tin or something.. lol.

have fun with the modeling, im still working on figuring that program out. Im going to have to see if there is a help file, so I can learn how to use it.
 

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and "M3" possibly anticipated 6volts.
Thats kinda what I meant by designing conservatively. Even 6 volt caps and diodes should be designed for a bit of overvoltage.
hen again a 3dc to dc5v converter would be overkill, or a few diodes as a voltage drop.
That just complicates everything. The old rule is KISS, Keep It Simple Stupid !. Heh.
have fun with the modeling, im still working on figuring that program out. Im going to have to see if there is a help file, so I can learn how to use it.
There is a help file in 4nec2. However, if you follow my directions here, you may be get to be further along the path to mastering 4nec2.
http://www.digitalhome.ca/forum/showthread.php?t=107457
 
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