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Discussion Starter · #1 ·
I have read about the Blake ( http://www.blake-aerials.co.uk/ ) JBX21 on postings from cymro. Sounds like a very directional, high-performance yagi.


cymro/Glenn: Any thing more to report? Our ears are burning! Is the JBX21 as good as it sounds? Is it better than the CM4228 & CM4248?


Has anyone else tried this 'aerial'? What are your results?


I live in San Ramon, CA. Mt. Diablo (elevation 3849 ft) sits between San Ramon and Sacramento. A coastal ridge sites between San Ramon and Sutro Tower in San Francisco. Needless to say, I need the best UHF antenna I can get.


Tom Lewis
 

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Tom,


I should be testing the Blake antenna within the next week. When I do, I will update my results on the Mt. Wilson OTA thread.


Glenn
 

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Discussion Starter · #3 ·
Glenn,


OK,


Thanks for the status. I will monitor that topic or course. Anyone else have any input in the the JBX21 (or the JKBX14)?
 

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I have tested the Antennacraft Maxus UHF Series #

MXU59 and can report much better results than with CM4248.


With a rotor (and up on the rooof rather than out a second story window) I'll bet I'll get everything..except Channel 36- KNBC-DTV is low on signal and highly indirect.


But,I can get 43.1,53.1,60.1,65.1,66.1


Murray Kerdman


Antennacraft Maxus UHF Series


Featuring quadrature drive that develops extended resonance and optimum impedance match across the entire UHF band, and a precision, stagger-tuned director array that produces compounded gain elevation!


MXU59


For Extreme Deep Fringe Areas


100" Boom Length


59 Electronic Elements


List Price $54.25
http://antennacraft-tdp.com/uhf.htm
 

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Discussion Starter · #5 ·
Murray,


So you got it, great. So, did you have a 4248 before and then replace it with the MXU59? Tell us the story, please.


How are the hills between Calabasas and the transmitter you are pointed to?


Tom
 

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I read about the Antennacraft Maxus UHF Series #

MXU59 on the web and wanted to compare it to the CM4248.


It has a rated average gain of 15db across the 14-69 UHF Band.


It is 100" long vs. the CM4248 80+/-".


NONE of the channels(which tonight also included 59.1 KCET-DTV) are being received directly from Mt. Wilson.


(NYPD Blue at 720P Upgraded to 1080i by the Sony HD100 looked particularly good)


As best as I can determine, I am getting reflected signals from my neighbors 30' high hillside across the street.


I believe that the antenna has high gain and a very narrow selective "rifle shot" pattern that rejects multipath well.


"Featuring quadrature drive that develops extended resonance and optimum impedance match across the entire UHF band, and a precision, stagger-tuned director array that produces compounded gain elevation!"


The only other antenna I am curious about and would love to try, even for a day, is the Blake ( http://www.blake-aerials.co.uk/ ) JBX21.


Any JBX21's available for such a high minded purpose in SFV/LA?


Murray Kerdman
 

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Glenn, where did you order the Blake antenna? Art

Quote:
Originally posted by Glenn_L:
Tom,

I should be testing the Blake antenna within the next week. When I do, I will update my results on the Mt. Wilson OTA thread.

Glenn
 

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Re JBX21WB


I ordered it by e-mail from the UK. I sent my credit card info to Blake by fax. The price, incl air freight, was about $140.00. It arrived in a few days after ordering. I did not have to pay any customs duty when it arrived.


The antenna is UHF only, and the specs. show a beamwidth of only 9 to 11 degrees, the narrowest I have seen specified outside of very expensive antennas. The gain is about 14 db ref to a dipole.


There are eight digital stations in LA. They are all on Mt. Wilson within about 2 miles of each other.


The towers are all about 30 miles away fro me, the bearings range from about 65deg to 66.5deg:


31: KTLA @ 66.0deg

36: KNBC @ 66.2deg

42: KWHY @ 66.0deg

43: KCAL @ 65.9deg

53: KABC @ 65.9deg

59: KCET @ 66.5deg

60: KCBS @ 65.1deg

65: KTTV @ 66.3deg

66: KCOP @ 65.7deg


There are also a few San diegoo stations:

19: KSWB @ 132 miles

23: XETV (FOX) @ 138 miles in Tijuana

25: ABC @ 112 miles

40: NBC @ 132 miles

55: CBS @ 112 miles


My location is topographically challenging. My antenna is on a rotor about 20 feet above the roof. It is not tilted.

I am using a Channel master preamp with a noise figure of 2.2db, and a gain of 23db. The look angle to Mt. Wilson is less than 2 degrees.


Unfortunately, there is a ridge about 500 yards from my house and the look angle to the top of the ridge is a liitle less than four degrees. (I got this from a software package I bought called "Terrain Navigator" which gives you the terrain profile along any bearing you care to choose).


Performance:


Analog UHF channels have multiple ghosts all across the screen, but the picture is watchable.


Ch31: I pick this up about 10% of the time

Ch36: I pick this up about 20% of the time

Ch42: I pick this up about 90% of the time

Ch43: I only saw this, briefly, on one occasion over the last year

Ch53: I pick tjhis up 100% of the time, but have occasional dropouts

Ch59: I pick this up 100% of the time, typically one or two glitches lasting a second oer two, every hour.

Ch60: I have never been able to pick this up

Ch65: I pick this up 100% of the time, no drop outs.

Ch66: I pick this up 100% of the time, no drop outs.


The antenna bearing has to be within about 3 to 5 degrees to get the above results. Outside this range I get no picture at all.


As for San Diego, I can sometimes pick up Ch 23 even with the antenna pointed at Mt. Wilson, which is a bearing discrepancy of 80 degrees!


On the few occasions that I rotate the antenna towards S. Diego, I pick up 19, 23, and 25 about 50% of the time, and 55 occasionally. I have never seen 40.


As Glenn mentioned, I am using a TU-DST50. I also use a DTC100. There is not a significant difference in performance.


When Glenn visits, I'll check out the 6000OTA performance and compare it with my tuners.


One of these days I am going to tilt the antenna a few degrees to see if that helps.


Have fun!

 

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In the U.S., TV channels 14 through 69 use 6 MHz wide segments of UHF frequencies between 480 MHz and 806 MHz.


I also know that in the U.K. their channels use 8 MHz wide segments of UHF frequencies. But, does anyone know what frequencies are covered? (This would help to compare those British aerials for usage here in the states.)


------------------

George at WNDU
 

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Art,


Tom is correct. I going to let cymro test my dish6000 to compare reception with his Panasonic STB TU-DST50 and he will lend me a spare Blake antenna to test. As far as I know, you will have to order it from the UK.


Murray,


What direction are you aiming the antenna in relation to the towers. I have found that the signal can bend over the top of a mountain quit a bit, but my antenna's always works best pointed in the direction of the tower. A large mountain range blocks my line of site with Mt. Wilson by at least 1,000'. I have never been able to pick up a reflected signal, too much competition with all the other multipath reflected signals.


Glenn
 

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Thanks cymro. From Blake-Aerials web page the U.K. UHF channels are numbered from 21 to 68 and they use the frequencies 470 to 853 MHz.


Band A Ch. 21 - 37 470 - 605 MHz. (U.S. Ch. 14-36)

Band B Ch. 35 - 53 583 - 733 MHz. (U.S. Ch. 32-57)

Band C/D Ch. 48 - 68 693 - 853 MHz. (U.S. Ch. 51-77*)


(*Originally U.S. UHF-TV channels were 14-83, 470-890 MHz., but channels 70-83 were reassigned to Cellular so now U.S. UHF-TV Channels are 14-69, 470-806 MHz, and U.S. UHF-TV Channels will be further reduced at the end of the DTV transition period to 14-51, 470-698 MHz.)


------------------

George at WNDU
 

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Glenn has now posted detailed results of a "fly-off" test between the JBX21WB and Channel Master 4248 yagi in the Mt. Wilson multipath discussion.


Specs as follows (4248 first, JBX21WB second):


Gain: 11.5db; 14db

F/B ratio: 15 to 24 db; 28 to 30db

Beamwidth: 20 to 42 deg; 9 to 11deg





[This message has been edited by cymro (edited 05-13-2001).]
 

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The weights of the Lindsay antennae are also interesting. Of course, for the price, I guess that I'd expect brick outhouse construction. Come on guys! Someone has to get a Zig Zag and report back to us http://www.avsforum.com/ubb/biggrin.gif



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The button is labeled "Play", not "Pay". STOP the MPAA!

Our Silent Angels
 

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The term "acceptance angle" refers to half the beam width angle. According to Blake, this is a common way of specifying antennas in the UK so they are obliged to specify this way also in order to remain competitive.


So, the JBX21WB has a beamwidth of 18 to 22 degrees.


However, this beamwidth is at the best spot in the spectrum; it is worse at other channels.


Channel Master specify beamwidth as a function of Channel number. For the 4248, the beam width varies from 42 degrees at Ch 14 to 20 degrees at Ch 69. If other antennas also vary considerably across the UHF band, then an antenna comparison chart would look very different.
 

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cymro,


I contacted Blake at their Sales e-mail address 3 days ago and no response yet,except their automated return e-mail stating that someone would contact me asap.


What should I do now?


Thanks


 

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MAX HD,


I telephoned them to get the info. about acceptance angle.


I spoke to Paul Blake at 011-44-114-275-9729


If you want sales call: 011-44-114-223-5000


To keep the cost of the call down. I use a dial around service so I prefix the above numbers with 1016868. The charge appears on your regular phone bill at 7.9c per minute. I don't know if this dial around is available in your area.
 
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