Need to Add VHF High Band to Existing DB8

JHB50 · 11-07-2009, 01:35 PM

Prior to the digital conversion date, I installed a DB8 (15.8dBi-2.2=13.6dBd) with a 7777 amp and got outstanding reception from LA which is 95 miles away but I have a good line down the pass between North Palm Springs and Mount Wilson.

If you reference http://www.tvfool.com/?option=com_wr...bc27780540b10a
or the attached .jpg you will see that for my location stations such as KNBC, KCBS and KOCE show NM's of ~ -27 and typically come in just fine.

KNBC right now shows a signal strength on my Sony of 78% and SNR of 23db, KCBS is marginal with 59% and 17db (but is usually better), and KOCE is at 81% annd SNR of 24db

The DB8 is however no good for VHF and so I no longer get KABC on 7 or KTTV FOX on 11 who have moved from their temp UHF physicals which also worked fine.

The table shows these stations with NM's of -11.5 and -7.1
which leads me to believe I should be able to get them with a reasonable highband VHF antenna connected to the VHF input of the 7777.

My 2 candidates are the YA 1713 which claims a gain of 9.1 - 10.3db although HDPrimer shows it only as 7.5dBd and the ClearChannel C5 which claims 8.4dBi or 6.2dBd.

My preference is the C5 since I am in the desert with high winds and have restricted space for a boom. My DB8 is mounted on a fence in a hotspot 5 feet above the ground facing an open golf course with no obstructions to the horizon. The C5 could be mounted in a similar fashion.

So the question is... will the C5 perform as well as the DB8 for those VHF channels given the higher NM but the lower antenna gain. The following relative calculations imply that it should.

ie: DB8 -27 + 13.6 = -13.4
1713 -11.5 +7.5 = -4.0
C5 -11.5 +6.2 = - 5.3

The second question is... will the hotspot for the vhf be wider(less sensitive that the uhf which currently is about 6 ") and give me more latitude.

Thanks for any advice before I order it.

aka.Hooper · 11-07-2009, 02:15 PM

Hello JHB50,

As an observation, you shouldn't even be able to get stations in the -27dB NM range at all, never mind "just fine"!!!

Obviously tvfool is missing something, and you're experiencing some freak occurrence.

That being said, I wouldn't make the assumption that whatever is happening is happening for VHF as well as the UHF frequencies, and thus your calculations:

Quote:

ie: DB8 -27 + 13.6 = -13.4
1713 -11.5 +7.5 = -4.0
C5 -11.5 +6.2 = - 5.3

may or may not be valid. (Though they are a logical reference.)

In conclusion I can be of little help to you, other than to say besides the fact that it has more gain, the 1713 is tried & true, and the Clearstream 5 is brand new & those gain #'s have yet to be confirmed in the real world...

Basically I just felt like typing.

JB Antennaman · 11-07-2009, 02:28 PM

I agree with Hooper.

You are probably going to need to get the VHF antenna up 35 feet off the ground to get any reasonable amount of reception.

projectsho89 · 11-07-2009, 08:11 PM

Quote:

Originally Posted by aka.Hooper

....and the Clearstream 5 is brand new & those gain #'s have yet to be confirmed in the real world...

Basically I just felt like typing.

They have been confirmed on my Sencore at around 6 dBd (or so) vs. a reference dipole made from 1/2" copper tubing, both with the same balun. I've used it to receive high-VHF channels out to about 80 miles (under good atmospherics) with a TVF forecast NM of less than 0.

If multi-path is likely to be an issue, the narrower BW of the 10-element Yagi can be beneficial.

In either event, the C5 is far friendlier from a size standpoint, but, you may need the couple of extra dB of gain from the bigger antenna.

Tower Guy · 11-08-2009, 02:05 PM

Quote:

Originally Posted by JHB50

My 2 candidates are the YA 1713 which claims a gain of 9.1 - 10.3db although HDPrimer shows it only as 7.5dBd and the ClearChannel C5 which claims 8.4dBi or 6.2dBd.

Third option: Antennacraft Y10-7-13.

Consider stacking two of them for more reliable performance.

My opinion is that the C5 isn't likely to work for you.

KenSoren · 11-09-2009, 05:21 PM

JHB50 - I have a question for you. I live in Yucaipa,which is 60 miles east of the LA towers so you are an additional 35 miles in the same direction - slightly south east through the Banning pass. A week ago last Saturday - when the north winds and cold front came through - I lost all my high VHF channels on my C4 and they stayed lost or really weak until mid-week, but then all the UHF channels were gone. Everything was back to normal by last Friday. Did you see the same? My C4 usually does a good job on the VHF and UHF stuff, but the last couple of weeks or so has been different.

By the way, most of the regulars on this forum say the C4 shouldn't work for the hi-VHF, but most of the time it outperformed a huge Channel Master that it replaced. I have a feeling that you are looking at the C5 because of it's size and lack of sharp elements. Because of my experience with the C4 I wouldn't be afraid of it because it is new.

JHB50 · 11-10-2009, 01:47 PM

Hi Ken:

We were away at that time so I cannot comment, however since the transition things are a lot worse for me. I am getting lots more dropouts on CBS with their move to 43, and I have totally lost KCET on 28. As well I have lost ABC and FOX who have gone to VHF which my DB8 will not get. Only positive is KNBC is perfect but I already have KMIR-NBC in Palm Springs so it doesn't give me much.

I am still trying to figure out what to do with VHF. ABC is broadcasting at 25kW on 7 and FOX at 15kW on 11. Since FOX has approval to go to 115kW, I am guessing that I won't be able to get it until that happens, and since ABC only has approval for 28.7 kW or just 25% of FOX, I'm wondering if I will ever be able to get it. Add to this the practical gain limitation of VHF antennas ~ 8dBd vs ~ 15 for UHF where 3dB is double the power, which means a VHF antenna will only get 1/4 of an equivalent UHF.

I will probably wait for FOX to do their upgrade and then order and test the C5, and return it if it does not work.

k2yi · 11-18-2009, 03:20 AM

Quote:

Originally Posted by JHB50

I will probably wait for FOX to do their upgrade and then order and test the C5, and return it if it does not work.

If there is an option to return the C5 anyway, why not purchase and test it now...you may be amazed at what you receive on VHF. Here in upstate N.Y., none of the VHF stations are running more then 12 kw, and every one is in the 70 to 80% SS, transmitters being 53 miles away.

11-07-2009, 02:28 PM	#3
JB Antennaman High Definition is the definition of life. Join Date: Jun 2009 Location: Jefferson County - Pennsylvania, high atop a hill Posts: 776	I agree with Hooper. You are probably going to need to get the VHF antenna up 35 feet off the ground to get any reasonable amount of reception. __________________ There is no exception for good reception!

11-09-2009, 05:21 PM	#6
KenSoren How can anyone watch standard def? Join Date: Jun 2009 Location: Yucaipa, CA - 60 miles east of LA Posts: 20	JHB50 - I have a question for you. I live in Yucaipa,which is 60 miles east of the LA towers so you are an additional 35 miles in the same direction - slightly south east through the Banning pass. A week ago last Saturday - when the north winds and cold front came through - I lost all my high VHF channels on my C4 and they stayed lost or really weak until mid-week, but then all the UHF channels were gone. Everything was back to normal by last Friday. Did you see the same? My C4 usually does a good job on the VHF and UHF stuff, but the last couple of weeks or so has been different. By the way, most of the regulars on this forum say the C4 shouldn't work for the hi-VHF, but most of the time it outperformed a huge Channel Master that it replaced. I have a feeling that you are looking at the C5 because of it's size and lack of sharp elements. Because of my experience with the C4 I wouldn't be afraid of it because it is new. __________________ Kenny S

11-10-2009, 01:47 PM	#7
JHB50 High Definition is the definition of life. Join Date: Nov 2006 Posts: 42	Hi Ken: We were away at that time so I cannot comment, however since the transition things are a lot worse for me. I am getting lots more dropouts on CBS with their move to 43, and I have totally lost KCET on 28. As well I have lost ABC and FOX who have gone to VHF which my DB8 will not get. Only positive is KNBC is perfect but I already have KMIR-NBC in Palm Springs so it doesn't give me much. I am still trying to figure out what to do with VHF. ABC is broadcasting at 25kW on 7 and FOX at 15kW on 11. Since FOX has approval to go to 115kW, I am guessing that I won't be able to get it until that happens, and since ABC only has approval for 28.7 kW or just 25% of FOX, I'm wondering if I will ever be able to get it. Add to this the practical gain limitation of VHF antennas ~ 8dBd vs ~ 15 for UHF where 3dB is double the power, which means a VHF antenna will only get 1/4 of an equivalent UHF. I will probably wait for FOX to do their upgrade and then order and test the C5, and return it if it does not work.