Bow Tie TV Antenna Designs (mclapp's M4 featured) - Page 44 - Canadian TV, Computing and Home Theatre Forums

Pafster · 2010-06-17, 12:18 AM

Hi all,
Very informative forum!

This is my first post but I've been reading alot since the last 2 years. Great work done, and cudos to all.
Now my question, I have built a m4 with 9.5"X9" elements and 1.75" phasing lines distance. i have tried it on a temporary pole a 20' without a reflector and I get all the channels except 27 when aimed a 170degrees. some are week but still lock. this is with a hrv950q on my laptop. I would like to know if I can
insert my reflector tubes (3/8" split tubes from my old 1978 VHF antenna that I dismantled) through the pcv pipe thaqt's 4" behind the elements or if they have to be completely exposed? I want to try 36" and only 8 rods positioned at 2" above and below each elements. Will passing them through the pvc pipe effectively make them 2 separate reflectors like the 4221hd or still 36"? If it makes them seperate grids would it reduce they're effectiveness?

Thanks for your time.

Paul

300ohm · 2010-06-17, 12:24 AM

Quote:

f I can
insert my reflector tubes (3/8" split tubes from my old 1978 VHF antenna that I dismantled) through the pcv pipe thaqt's 4" behind the elements or if they have to be completely exposed?

That would be fine. Only a very short piece is touching the plastic pipe. That would have very little effect on the velocity factor of the reflector rod.

Pafster · 2010-06-17, 12:35 AM

Thanks for the quick response

Quote:

Originally Posted by 300ohm

That would be fine. Only a very short piece is touching the plastic pipe. That would have very little effect on the velocity factor of the reflector rod.

Well the pvc pipe is ~3/4" od. You think that it won't make much difference?
I'll try to post picts when everything is finished. TVFool link:

http://www.tvfool.com/?option=com_wr...9fbe4798685b7b

Paul

300ohm · 2010-06-17, 02:46 AM

Quote:

You think that it won't make much difference?

Nope, not anywhere near what other building differences could make, heh.

mclapp · 2010-06-17, 12:57 PM

byebye_cable,
I'm not sure what you mean by looped but a 9" bay spacing needs a wire 28" long for each phase line before bending the twists. That measuremnet is for making a 9 1/2" x 9" with the long twist phase line. Add 1 1/2" for a 9 1/2" bay spacing (10"x9 1/2") and subtract 1 1/2" for a 8 1/2" bay spacing 9"x8 1/2").

I've used PVC pipe for spacers 3/4" works good but larger is ok, smaller will give clearance problems with the phase line twist and the mounting spine.

byebye_cable · 2010-06-18, 06:50 PM

Thanks Mclapp. Do you loop the phase line around the screw where it connects with the wiskers? (that is what I meant).

Also - forgive me as this is probably answered somewhere - but for the 9/8.5 M8 version, flat whiskers (not swept forward or back), flat reflector (mainly for higher uhf want wideish field of view) what is the correct distance between the whiskers & the screen? If that measurement is on your site I don't see it.

byebye_cable · 2010-06-19, 08:33 PM

Never mind about the looping the phase line question - I must have read that in a different thread - maybe the GH thread.

Still wondering about the correct separation between whiskers & screen.

mclapp · 2010-06-21, 09:59 AM

4" to 5" is a good reflector spacing for UHF and a narrow rnge of VHF-hi.

Pafster · 2010-06-22, 11:30 PM

I have just uploaded a few pics of my new M4 with alum rods as reflectors
pointed at 190deg I get all the u/s HDchannels plus the 4 hd from Montreal which is at 320deg so almost 140deg to the back. Analog channels are all
snowy. So I might build a second one and point it at Montreal. It's been up since friday night 18th june and never a drop in signal off the LG 55LD560 120mhz. the picture quality is amazing.

http://www.digitalhome.ca/forum/album.php?albumid=540

Paul

mclapp · 2010-06-24, 12:37 PM

Pafster,
Looks good, I like that looped back PVC frame for mounting the reflector rods.

Pafster · 2010-06-25, 09:42 AM

Thank you mclapp.

Mounted on my tower at ~45' . I tried 3 different models of the SH by OTA canuck, but the results were not very good, so I decided to build your 2 bay with whiskers and it picks up all the HD channels and local SD channels with very good picture quality!

This is a 10"X9.5" and 8" center whiskers. And a temporary mount at 20'. I will make a permanent mount on the old 1"X1" boom tube and will put it up over the M4 pointed at 320deg. I just don't know which spacing should be used between the 2 and hooked up together. I do not have a preamp. I want to feed 2 htpc's and 3 tv's.

Should I just run 2 rg6 cables down the tower and use the M2/whiskers split 2 way to the pvr's and the M4 feed to the 3 tv's with a dist amp?
I have a brand new CM rotor but I don't want to use it, it will be up for sale.

The signal is steady at 100% on all HD channels except WVNY ABC which is between 60 and 75% all the time. This is channel 13 that everyone has trou ble with, this is off the M4. The M2 picked it up at 18-23% on the temp mount which the M4 could not see at all at the same height. I'm sure the M2 will be as good up over the M4 on the tower.

What do you think would be best for a good signal? Should I order a preamp and join the 2 on the tower? I don't want to keep going up there all the time to make changes, so if a preamp is recommended I'll instal it at the same time as the M2.

Thanks again for all your time and efforts.

Paul

mclapp · 2010-06-25, 12:40 PM

Glad the M2 center whisker is working for you that's the first field test I've heard of. I have one built for field testing but haven't had time to get up there and do a proper test to do it yet.

As far as combining antennas goes it's going to be difficult to do without some sort of loss. Combining 2 antennas into the same common cable other than stacking 2 exact same antennas is a crap shoot, sometimes under the right signal combinations it can work but almost always at the expence of signal strength on one channel or another. The best way would be to amp the antenna with the weaker signals and combine them at the house with an A-B switch or use one to feed som and one to feed the others as you suggested. You may be able to use a simple combiner in place of the A-B switch but it will usually cause some sort of loss not from the combiner but from the signals combining in a bad way. It's worth a shot, from that point you may need a distro amp to feed all your receivers but that really depends on signals strengths.

Pafster · 2010-06-25, 06:43 PM

I'll set it up permanently tomorrow if it doesn't rain to hard. I'll run another cable and bring it in the other side of the house where the pvr's are. It will be up around 50' and i'll test the signal once split to 2 outs. This one will probably be strong enough not to need a amp. We'll see when it's done. I will put the amp on the other line that will be split to 3 outlets. and check them also. I posted 2 pictures of it on the temp setup if you want to have a look. I'll clean up the setup when I install it on it's permanent post.

I'll post a few more picts when it's up on the tower and let everyone know how the signal is once they're split.

Paul

Pafster · 2010-06-27, 12:24 AM

Here it is M2/whiskers stacked over the M4 with separate cables. It's 49'9" off the ground. Channel 13 WVNY DT ABC still does not lock but it's 170deg to the rear so it's not a big issue since it is rock solid on the M4. All the other channels come in over 55% and all the sd channels except 62 cjnt are very clear, it even picks up PBS 57.x at 90 deg and Sherbrooke stations very watchable at 150deg from 65miles away. Excellent results for a small reflectorless HD antenna. Thanks mclapp!

Notice the little bird in the picture

It's one of the many hummingbirds that use the antenna as a perch.

Paul

mclapp · 2010-06-28, 11:53 AM

Nice picture, I'm glad someone gave the M2 center whisker a try.

My idea with that antenna was to come up with something that had moderate gain but was small for urban/suburban use especially where larger antennas may not be allowed. The VHF-hi reception is improved over a standard 2 bay although still by no means great, it could be good enough for urban use.

2010-06-17, 12:18 AM	#646
Pafster Rookie Join Date: Jun 2010 Location: Laprairie , QC. south shore of Montreal Posts: 7	reflector question Hi all, Very informative forum! This is my first post but I've been reading alot since the last 2 years. Great work done, and cudos to all. Now my question, I have built a m4 with 9.5"X9" elements and 1.75" phasing lines distance. i have tried it on a temporary pole a 20' without a reflector and I get all the channels except 27 when aimed a 170degrees. some are week but still lock. this is with a hrv950q on my laptop. I would like to know if I can insert my reflector tubes (3/8" split tubes from my old 1978 VHF antenna that I dismantled) through the pcv pipe thaqt's 4" behind the elements or if they have to be completely exposed? I want to try 36" and only 8 rods positioned at 2" above and below each elements. Will passing them through the pvc pipe effectively make them 2 separate reflectors like the 4221hd or still 36"? If it makes them seperate grids would it reduce they're effectiveness? Thanks for your time. Paul

2010-06-22, 11:30 PM	#654
Pafster Rookie Join Date: Jun 2010 Location: Laprairie , QC. south shore of Montreal Posts: 7	Pictures in M4 build album I have just uploaded a few pics of my new M4 with alum rods as reflectors pointed at 190deg I get all the u/s HDchannels plus the 4 hd from Montreal which is at 320deg so almost 140deg to the back. Analog channels are all snowy. So I might build a second one and point it at Montreal. It's been up since friday night 18th june and never a drop in signal off the LG 55LD560 120mhz. the picture quality is amazing. http://www.digitalhome.ca/forum/album.php?albumid=540 Paul

2010-06-27, 12:24 AM	#659
Pafster Rookie Join Date: Jun 2010 Location: Laprairie , QC. south shore of Montreal Posts: 7	Here it is M2/whiskers stacked over the M4 with separate cables. It's 49'9" off the ground. Channel 13 WVNY DT ABC still does not lock but it's 170deg to the rear so it's not a big issue since it is rock solid on the M4. All the other channels come in over 55% and all the sd channels except 62 cjnt are very clear, it even picks up PBS 57.x at 90 deg and Sherbrooke stations very watchable at 150deg from 65miles away. Excellent results for a small reflectorless HD antenna. Thanks mclapp! Notice the little bird in the picture It's one of the many hummingbirds that use the antenna as a perch. Paul Last edited by stampeder; 2010-06-27 at 11:05 AM. Reason: image link fixed

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2010-06-17, 12:57 PM	#650
mclapp Join Date: Aug 2008 Location: Upstate NY Posts: 597	byebye_cable, I'm not sure what you mean by looped but a 9" bay spacing needs a wire 28" long for each phase line before bending the twists. That measuremnet is for making a 9 1/2" x 9" with the long twist phase line. Add 1 1/2" for a 9 1/2" bay spacing (10"x9 1/2") and subtract 1 1/2" for a 8 1/2" bay spacing 9"x8 1/2"). I've used PVC pipe for spacers 3/4" works good but larger is ok, smaller will give clearance problems with the phase line twist and the mounting spine.

2010-06-18, 06:50 PM	#651
byebye_cable Join Date: Nov 2009 Location: Toronto Posts: 434	Thanks Mclapp. Do you loop the phase line around the screw where it connects with the wiskers? (that is what I meant). Also - forgive me as this is probably answered somewhere - but for the 9/8.5 M8 version, flat whiskers (not swept forward or back), flat reflector (mainly for higher uhf want wideish field of view) what is the correct distance between the whiskers & the screen? If that measurement is on your site I don't see it.

2010-06-19, 08:33 PM	#652
byebye_cable Join Date: Nov 2009 Location: Toronto Posts: 434	Never mind about the looping the phase line question - I must have read that in a different thread - maybe the GH thread. Still wondering about the correct separation between whiskers & screen.

2010-06-21, 09:59 AM	#653
mclapp Join Date: Aug 2008 Location: Upstate NY Posts: 597	4" to 5" is a good reflector spacing for UHF and a narrow rnge of VHF-hi.

2010-06-24, 12:37 PM	#655
mclapp Join Date: Aug 2008 Location: Upstate NY Posts: 597	Pafster, Looks good, I like that looped back PVC frame for mounting the reflector rods.

2010-06-25, 09:42 AM	#656
Pafster Rookie Join Date: Jun 2010 Location: Laprairie , QC. south shore of Montreal Posts: 7	Thank you mclapp. Mounted on my tower at ~45' . I tried 3 different models of the SH by OTA canuck, but the results were not very good, so I decided to build your 2 bay with whiskers and it picks up all the HD channels and local SD channels with very good picture quality! This is a 10"X9.5" and 8" center whiskers. And a temporary mount at 20'. I will make a permanent mount on the old 1"X1" boom tube and will put it up over the M4 pointed at 320deg. I just don't know which spacing should be used between the 2 and hooked up together. I do not have a preamp. I want to feed 2 htpc's and 3 tv's. Should I just run 2 rg6 cables down the tower and use the M2/whiskers split 2 way to the pvr's and the M4 feed to the 3 tv's with a dist amp? I have a brand new CM rotor but I don't want to use it, it will be up for sale. The signal is steady at 100% on all HD channels except WVNY ABC which is between 60 and 75% all the time. This is channel 13 that everyone has trou ble with, this is off the M4. The M2 picked it up at 18-23% on the temp mount which the M4 could not see at all at the same height. I'm sure the M2 will be as good up over the M4 on the tower. What do you think would be best for a good signal? Should I order a preamp and join the 2 on the tower? I don't want to keep going up there all the time to make changes, so if a preamp is recommended I'll instal it at the same time as the M2. Thanks again for all your time and efforts. Paul

2010-06-25, 12:40 PM	#657
mclapp Join Date: Aug 2008 Location: Upstate NY Posts: 597	Glad the M2 center whisker is working for you that's the first field test I've heard of. I have one built for field testing but haven't had time to get up there and do a proper test to do it yet. As far as combining antennas goes it's going to be difficult to do without some sort of loss. Combining 2 antennas into the same common cable other than stacking 2 exact same antennas is a crap shoot, sometimes under the right signal combinations it can work but almost always at the expence of signal strength on one channel or another. The best way would be to amp the antenna with the weaker signals and combine them at the house with an A-B switch or use one to feed som and one to feed the others as you suggested. You may be able to use a simple combiner in place of the A-B switch but it will usually cause some sort of loss not from the combiner but from the signals combining in a bad way. It's worth a shot, from that point you may need a distro amp to feed all your receivers but that really depends on signals strengths.

2010-06-25, 06:43 PM	#658
Pafster Rookie Join Date: Jun 2010 Location: Laprairie , QC. south shore of Montreal Posts: 7	I'll set it up permanently tomorrow if it doesn't rain to hard. I'll run another cable and bring it in the other side of the house where the pvr's are. It will be up around 50' and i'll test the signal once split to 2 outs. This one will probably be strong enough not to need a amp. We'll see when it's done. I will put the amp on the other line that will be split to 3 outlets. and check them also. I posted 2 pictures of it on the temp setup if you want to have a look. I'll clean up the setup when I install it on it's permanent post. I'll post a few more picts when it's up on the tower and let everyone know how the signal is once they're split. Paul

2010-06-28, 11:53 AM	#660
mclapp Join Date: Aug 2008 Location: Upstate NY Posts: 597	Nice picture, I'm glad someone gave the M2 center whisker a try. My idea with that antenna was to come up with something that had moderate gain but was small for urban/suburban use especially where larger antennas may not be allowed. The VHF-hi reception is improved over a standard 2 bay although still by no means great, it could be good enough for urban use.