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Old 4-Aug-2013, 12:23 AM   #50
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 123
Quote:
Originally Posted by Pete Higgins View Post
...This is starting to remind me of a time when we listened to the radio every Saturday night for the next installment of Boston Blackie or the Shadow –great stuff.
Yep. “…return with us now to those thrilling days of yesteryear!…” .

Listened to radio shows such as: Dragnet, Suspense Theater, Gunsmoke, and the Lone Ranger.

Quote:
Yesterday, Time Warner dropped KCBS {RF 43}...
They dropped KTVT (CBS) here in Dallas. Such as this, may in long run be good for all broadcasters.

Quote:
OTA, I get 9 pretty reliably but CBS {RF 43, 2- Edge with a Noise Margin of -22.1 dB @ -112.90 dBm} comes & goes especially during late afternoon early evening hours. Do you think I would see any improvement swapping out my 91XG’s PCT MA2-M 2.7 dB NF amplifier with one of the new Winegard LNA-200’s that they claim has a 1 dB NF on UHF? Or would the improvement be “in-the-noise” –so to speak?
Hard to say.

Seems as any improvement could help with such a low signal level.

Based on my measurements of industrial/commercial drop amplifiers, of which your PCT MA2-M is one, the specified noise figure of the PCT MA2-M is probably realistic. So, if Winegard LNA-200 specifications are accurate, you could see approximately 1.7 dB improvement in S/N ratio. That is worthwhile, especially in a low signal situation as you describe.

Small improvements, even if they do not entirely eliminate dropouts, can reduce dropout time duration. On the other hand, if the dropouts are a result of severe multipath, signal level increases often have less noticeable effect.

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On Winegard LNA-100 and LNA-200 specifications: It is plausible that all the specifications are accurate. The information provided by Winegard suggest a design using pHEMT transistor or IC. With such GaAs FET devices available these days, all Winegard’s specifications are within reason, and preamplifiers using such devices could be manufactured at low enough cost to enable mass marketing.

The thing to watch for in pHEMT based preamplifiers is susceptibility to atmospheric discharge. To a large degree this problem is solvable, hopefully Winegard has done so.

Of course if Winegard's specifications are not accurate, as seems sometimes, then the above speculations are meaningless.

Couple of ways to help answer such questions:

- Test the preamplifier to see if it meets specifications.
- View the layout of the circuit to identify the class of active devices.

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Pete, in your situation, I would probably give it a try, and be prepared to add it to my collection of interesting but maybe not very useful preamplifiers.

Note: Based on ADtech's comment in another forum, the LNA-200 may be more like Winegard's previous preamplifiers. In such a case, it is unlikely the preamplifier would help your reception.

Last edited by tripelo; 4-Aug-2013 at 12:39 PM. Reason: Add addition end comment and Note
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