Antenna help 50 miles south of Seattle - Page 3

IDRick · 10-16-2009, 06:06 PM

Just a quick follow up, beamwidth is very crucial for those of us with towers in divergent directions (70 degrees in my case). I have attached my data comparing a 4-bay mclapp DIY antenna with flat elements versus one with swept back elements. Clearly, sweeping the elements back saves margin (or gross signal strength) over flat elements.

IMO, these data are also helpful for understanding what happens to channels off direct axis. In my situation, aiming the antenna 35 degrees off axis results in a 4 to 5 dB decrease in margin. This is a big hit but not necessarily a game breaker... My stations all have NM's in excess of 40 dB's so they can take this small hit and still have plenty of signal strength.

EscapeVelocity · 10-16-2009, 06:20 PM

Hey, that's a great chart, thanks for sharing your measurements.

Yeah, lets think about that for a minute.

If I have Antenna #1 with 12 dBd gain and another Antenna #2 with 8 dBd gain, and the 12 dBd gain antenna has a 50 degree beamwidth and the 8 dBd has a 70 degree beamwidth.

At 25 degrees of azix Antenna #1 beats Antenna #2 even at 3 dBd down from maximum forward gain. At 35 degrees off axis Antenna #1 may or may not beat Antenna #2.....depending on how sharp #1 is approaching a null or some such.

So...

EscapeVelocity · 10-16-2009, 06:44 PM

You cant assume a linear regression from the beamwidth numbers.

In other words, with Antenna #1 you cant assume that another 25 degress out another 3 dB down.

Don_M · 10-16-2009, 07:20 PM

Saw this post first thing today and meant to respond, but then got called away. Sorry for the delay.

Quote:

Originally Posted by Bobross

So this amp goes up with the antenna on the pole or can I put it in the atic on a short lead?

The best location is up on the pole right next to the antenna, but putting it on a downlead of less than 25 feet should work OK. The pre-amp's power injector has to go inside near a power source, and it's important to connect the coax downlead directly form the pre-amp to the power injector. (There are different ways of doing it, but that would kick off a whole new discussion

.)

Quote:

Since I have your ears, what converter box should I be hunting for? I see mention of ones pulling in channels at lower strength. Some as low as 25%. I bet you guys have opinions about that. thanks

The Insignia, Zenith DTT 901, Zinwell 970A, DTVPal and Digital Stream boxes typically get the most props for good performance. Please know that they're getting harder to find both in stores and online as more time elapses since the transition. We have a list of box auctions here.

EscapeVelocity · 10-16-2009, 08:28 PM

Bob, what converter box have you decided on?

Bobross · 10-16-2009, 08:42 PM

I am leaning towards the dtvpal for its guide mostly at least for the first box. I will get it going with that then decide whether a cheaper one will do for the bedroom tv.
I was about to order the Winegard hdp-269 and the Winegard HD7696P and saw the Winegard HD7697P and got to wondering. Actually the specs were only slightly better. Any comments ?

EscapeVelocity · 10-16-2009, 09:07 PM

Make sure you get the DTV Pal PLUS which is different from the DTV Pal. The PLUS version has a more sensitive tuner.

Don_M · 10-17-2009, 11:08 AM

Quote:

Originally Posted by Bobross

I was about to order the Winegard hdp-269 and the Winegard HD7696P and saw the Winegard HD7697P and got to wondering. Actually the specs were only slightly better. Any comments ?

You might be on to something: For an extra dozen bucks, you get roughly a full dB higher gain by moving up from the 7696 to the 7697. That's more significant than the half-decibel-or-so increase between the 7697 and the 7698, for which you'll pay almost $40 more. On the basis of value, it's worth the additional cost. Remember, the antenna should last for a couple of decades, so the difference is pennies per year.