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Discussion Starter · #1 ·
Hi all,


From Ch 14 up to around Ch 35 the Blake "aerial" was a clear winner.Analog channels were cleaner and DT channels were 5-10pts.higher as measured on the DTC-100.


As an added benefit,with a full range VHF/UHF preamp,it does a good job on VHF also.Just have to point it at an oblique angle to the transmitters.


At 13-1/2ft.long it's not small by any means,but has probably less than half the windload of the CM Dish.Frees up additional mast space for other antennas I been wanting to put up on the tower.


Could be a problem solver for fringe viewers wanting lower UHF DT channels.


As a side note,as I was doing a little Dx'ing early Saturday morning,it helped ID a station that was unwatchable on the Dish.Ch28 WHWC (PBS),Menomonie,[email protected]


I also have another Blake model I will be testing in the next few weeks(JBX21C-D) against the Dish on the higher UHF channels.
 

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Wow! 512 miles has to be a new record!


How does the performance of the A version tail off as you approach channel 69? Also, do you have spec tables for gain vs. channel for the A as well as CD versions?


Congratulations again on your super-DXing.


Steve
 

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Great news !!! I am super excited as I just ordered some JBX21B antennas about a week ago to try to get ch 57 better from NH.


Also note to anyone interested in these: Blake reports shipping cost is for 1 to 25 antennas, so group purchases would be a good idea, till some US distributor starts to carry these.

 

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Quote:
Originally posted by Cornell77:
Wow! 512 miles has to be a new record!


How does the performance of the A version tail off as you approach channel 69? Also, do you have spec tables for gain vs. channel for the A as well as CD versions?


Congratulations again on your super-DXing.


Steve


The Blake web site has lots of info:


blake-aerials.co.uk
 

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Hello Greg,


Can you combine the DY28A (channels 14-35) with the CD version antenna (channels 50-77) and still get coverage of the missing UHF middle (channels 36-49)?


In other words, will the out of range coverage still be good enough?


Steve

 

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Hi,

The Blake Aerials on some of there models come in wide band versions that cover all the US UHF band. I have a JBX-21W/B. Have not tried it yet because I installed a APS U92 about 4 months ago and it has been a perfect antenna for digital reception. Both the Blake JBX-21 and the U92 share some features. The biggest one is the fact that both use dual sets of elements, essentially two antennas on one boom. If you look at the Blake you will find that the driven elements are actually two dipoles joined at a common feed point. The APS does the same, except all the elements top and bottom are all active. This is the part that makes the APS work so well. it is virtually flat across the entire UHF band and some. The Blake and the APS share a narrower vertical beam width due to the dual row of elements. This is a key feature that reduces multi-path problems very well. The APS is also better from a point of view of impedance matching. It has a resistively terminated feedline. This keeps internal reflections down to nothing. You can see this in the picture on analog stations. I hope that some of you will try these two antennas. I hope to get the Blake up this weekend.


pat


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HDjunky
 

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Pat,


Glad to hear you are comparing Blake and the APS around here! The Blake B group (jbx21B) was my choice to try next since I only need super gain at ch 57 and can even benefit from a cut around ch 25 which I now have to filter out so my preamps don't overload.


I'll get a Lindsey or Wade when I win a lottery, but meanwhile that APS looked like my only other choice to try!

I've already been through the regular stock antennas from Winegard and Channel Master.



So how's your reception on ch 57 WENH-DT?
 

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Hi,


I looked on the APS website and I could only find FM antennas there.


Where can I find specs on the U-92 that you have?


I have a Blake JBX21WB which works pretty well in a topographically challenged location: no line of sight, 2 degree look angle to xmitters 30 miles away, but 4 degree look angle to ridge between my location and the xmitters.


Look fwd to your comparison test of APS U92 vs. Blake


As to the Blake dy28, it is designed for customers in Souther Ireland who wish to pick up BBC-TV from transmitters in South West Wales, a distance of over 100 miles. I suspect that the dy28 does not have such a good vertical bw as the JBX21WB, even though it has higher gain.


To Art who asked me about recent experience with the JBX21WB, I received an updated dipole with updated balun together with a larger reflector from Blake. The new components gave a few points additional signal quality on the RCA DTC100. I then tilted the antenna somewhat above the ridge line and got a further few points improvement. In addition, Ch60, which never previously registered when I scanned for channels, now registers during the scan but only at around 23%; not enough for a picture. I use a Channel Master 7778 low noise preamp.


However, I still suffer dropouts every now and again on the channels that I do receive. I have hopes that the new generation tuners will overcome the dropouts.


I did have a brief opportuniy to try out a 6000 rcvr (thanks to Glenn L) and we managed to get an occasional frozen picture from NBC San Diego - a distance of 132 miles - on Ch40. I frequently pick up the higher power S. Diego channels with the DTC100. This is significant in that Ch40 is operating at a much lower power than the LA channels.


Thanks


[This message has been edited by cymro (edited 10-01-2001).]


[This message has been edited by cymro (edited 10-01-2001).]
 

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jhe and cymro

Below is the URL for APS.
http://www.antennaperformance.com/new/


The U92 which is mounted 25 feet off the ground on a rotor and fed with good quality RG6, about 60 feet worth. No pre-amp is used. For WENH-DT in NH (40 miles), I get a consistent 76 on the DTC-100. Only seen 2 dropouts in 2 months. All other channels in Boston area, are high 90s, except for FOX which is now 60 and was in the 80s.

I also went through Winegard and Channelmaster. Their technology is not up to what I see in the APS. The Blake is mostly traditional Technology. My concerns are with internal reflections (high VSWR) in the feed system. I noticed this especially with the Winegard CA-9095 which I used for a long time. You can tell sometimes looking at an analog station by noticing that you can't get rid of shadows in the picture. I used to get lots of dropouts on that antenna. With the U92 you will see the difference on the analog stations, when you aim it, all shadows disappear. You have to look real close to see any. This I think has a great bearing on how well you receive digital signals. If you have a Hi VSWR condition then the internal reflections will hurt your digital reception. This is before you even deal with natural reflections from the environment. I will let you know how I make out with the Blake.


Pat
 

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cymro,


Thanks for the update. I'll watch this thread. For anyone else here: I just got a JBX21WB antenna (oops - aerial)to receive stations from a distance of only about 60 miles. I've replaced my ChannelMaster 4248. I'm also using a CM 7775 preamp/amp.


I see only a little improvement. Looking at an analog uhf station in the same location as a group of digital towers, I get lots of ghosts, both leading and trailing ghosts. My dtv signals come and go. It's rare to be able to watch for an hour without any dropouts.


I have the antenna tilted upward slightly.


Art

Anacortes, Washington
 

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Patjoy, What VSWR? What are the implications? Art

Quote:
Originally posted by patjoy:
jhe and cymro

Below is the URL for APS.
http://www.antennaperformance.com/new/


The U92 which is mounted 25 feet off the ground on a rotor and fed with good quality RG6, about 60 feet worth. No pre-amp is used. For WENH-DT in NH (40 miles), I get a consistent 76 on the DTC-100. Only seen 2 dropouts in 2 months. All other channels in Boston area, are high 90s, except for FOX which is now 60 and was in the 80s.

I also went through Winegard and Channelmaster. Their technology is not up to what I see in the APS. The Blake is mostly traditional Technology. My concerns are with internal reflections (high VSWR) in the feed system. I noticed this especially with the Winegard CA-9095 which I used for a long time. You can tell sometimes looking at an analog station by noticing that you can't get rid of shadows in the picture. I used to get lots of dropouts on that antenna. With the U92 you will see the difference on the analog stations, when you aim it, all shadows disappear. You have to look real close to see any. This I think has a great bearing on how well you receive digital signals. If you have a Hi VSWR condition then the internal reflections will hurt your digital reception. This is before you even deal with natural reflections from the environment. I will let you know how I make out with the Blake.


Pat
 

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Discussion Starter · #12 ·
Hi guys,


As I was anxious to see how both Blakes'covered the whole UHF band,I removed the Dish yesterday and added the JBX21C/D.


The JBX21 seems to do well down to Ch35,where the DY28 falls off rather sharply.Above Ch50 on the DY28 it's hit or miss,mostly miss.


I think I'm getting close to the ultimate "DX machine",but I won't know for sure until Friday,when I put the Dish back up to do a direct comparison to the JBX21.A relatively easy job with the fold-over crankup tower.


BTW,I had a U-92 that I used last Winter and it worked very well.I liked it better than the CM4228 it replaced.
 

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Max,


Would you mind explaining this in a little more detail?


"As a side note,as I was doing a little Dx'ing early Saturday morning,it helped ID a station that was unwatchable on the Dish.Ch28 WHWC (PBS),Menomonie,[email protected]"




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-Glenn
 

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Discussion Starter · #14 ·
Hi Glenn,


Before I go to work every morning I turn the TV on while I'm having a cup of coffee and check for enhanced propagation of TV signals (Dxing).I had the antenna array pointed to the northwest with the DY28 as the feed antenna and as I rotated it to the north I picked up KFXA-28 Cedar Rapids,Iowa (373mi.).Then I moved it further north and noticed a weak PBS station with a promotional format that was unlike any that I had ever seen locally.More upbeat.

At that point I switched the feed to the CM dish and it was too snowy to make an ID.

Both antennas were on the same mast with the smaller DY28 on top.Used a CM7777 on the DY28 and a CM7775 on the CM Dish.RG-11 coax on both,except for the output from the DY28.It's not made to accept the larger cable.


I suppose the advertised increase in gain of around 3-4db made the difference.


I will admit the DY28 was about 7ft.higher in elevation,but I was pressed for time getting to work and didn't have time to adjust tower height for an exact comparison.
 

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Discussion Starter · #15 ·
BTW,

Just before I wrote the previous post I logged Detroit 14-1 on the DY28,44-1 on both,and 58-2 on the JBX21 C/D. (245mi.) It's late and I'm going to bed.


Good Nite!
 

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Max hd

Before i go to work.....

I take out the trash......

You lucky Dog

woo-


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Studio Broadcast Engineer

KET
 

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Art,

VSWR stands for "voltage standing wave ratio" and is a measurement of how much signal is reflected in the feed system and it's load. What that means is how the electrical signal induced in the antenna by the RF from the transmitter and sent down the feed line to the receiver reacts to inconsistent impedance. Theoretically the antenna should present a consistent impedance of 300 or 75 ohms, depending on antenna design and feed line type used, across the entire range of frequencies or channels. This does not happen in the real world, and is influenced by the design of the antenna. The feed is usually a reasonable constant, but also varies, again because nothing is perfect. Comparing antennas like the APS and the Blake, you have to take a good look at how the driven elements (the ones that feed the signal to the receiver) are designed. The Blake is nothing but a dipole and not even one that is well compensated to give it a wider band width. The APS uses every element as a driven element and is coupled to the feed line via capacitive and inductive coupling. Each element also covers a part of the UHF band. I believe each element is a full wave loop, in itself fairly broad banded. This antenna is broad enough to cover the high end of the VHF band all the way down to ch 7. In this case the elements really work as half wave loops. It's a real nice design and lends itself to real good performance in the face of multi-path. Since the design has real good impedance control, you don't have to worry about internal reflections making it hard to receive digital signals. This I believe, is what happens to many older designs and what makes the APS perform very well. The two rows of elements also gives the antenna a narrower vertical beam width. Just a few degrees reduction is enough to reduce significant ground reflected multi-path. This was a bit more then the original question, hope it did answer your question.


Pat


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HDjunky
 

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Woowoo,

yes, I agree with you, from the point of view that Standing waves will cause serious if not destructive problems with your transmitter. In the case of reception the problem is very subtle. In the era of analog TV it was not much of a problem, but with the advent of DTV in the form of 8VSB it has become in my mind an important design issue. Any amount of distortion you do to the modulated 8VSB signal will have detrimental effects on the ability of the receiver to demodulate it. Distortion is additive and the less distortion you create the better chance of demodulating.


Pat


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HDjunky
 

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Hi Art,

Yes they are orientated vertically, but it is a horizontally polarized antenna. It is basically two antennas stacked together connected to a single transmission line. The transmission line is actually terminated with a resistor. The resister effectively terminates the transmission line. The antenna impedance is 300 ohms so you will need a matching transformer to go to 75 ohm coax. I believe one come with the antenna.


Let me know how you make out with it if you get one.


Pat


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HDjunky
 
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