Bow Tie TV Antenna Designs (mclapp's M4 featured) - Page 78 - Canadian TV, Computing and Home Theatre Forums

mclapp · 2012-04-22, 10:29 PM

For the reflector you can start out flat, if you need alittle more you can go to the curve or angled style for an improvement on UHF. Flat, angled, or curved will work the same on VHF-hi just make sure it's over 32 inches wide for Channel 13 but wider will be ok.

fireflimoon · 2012-04-23, 06:03 PM

Thanks McLapp, (another question for you or anyone else who knows)

If I wanted to vertically stack two m4's for ch 43 would the 9.5 x 9 be much better or worse than the other variants? I mean, how would the 9.5 x 9 compare to a m8 stack optimized for ch 43? Are we talking more than a couple db's or less than that?

Thanks for the feedback...

BOUVAL · 2012-04-23, 08:28 PM

Fireflimoon,

Before stacking, you should try a reflector with your m4, like some cardboard wrapped with alum foil 4~5 inches behind the M4.

Have you tried a pre-amp.

Is it for Rawdon or Pointe-Claire ?
.

fireflimoon · 2012-04-23, 10:15 PM

Hi Bouval,

It's for Rawdon but testing here first. I put 9 (4" inches apart) curved reflectors that came from an above ground pool that was brought down - pretty amazing how much aluminum you can find in that mess after you tear it down. So I an not sure how good they are as reflectors - but I am assuming they are aluminum if not galvanized but light.

The rods are 46 inches long and curved. I slapped them on sloppy - not exactlt straight but just to test this evening.

For some channels the reception was better than the gh4 in the attic - this one is on the second floor of the house.

The curve comes from the fact that the "rods" were corner pieces of the pool and they acted as clamps somewhat for the vinyl of the pool at the top.

Anyhow, it is for Rawdon. The thing about the M4 is that it can be stacked which isn't possible for Nikiml's GH designs which I really like. The channels that would be of interest are the Mount Mansfield channels and the PBS (VPT and Mountain Lake) but it is a stretch from there to Rawdon, so gain is important.

I'm willing to give it a shot for ch 43 even though it has been mentioned that it is far.

http://www.tvfool.com/?option=com_wr...7fcf06b2676ae0

Thanks

fireflimoon · 2012-04-23, 10:32 PM

By the way, I know I am not using the optimum materials yet ...

300ohm · 2012-04-23, 10:51 PM

Quote:

pretty amazing how much aluminum you can find in that mess after you tear it down. So I an not sure how good they are as reflectors - but I am assuming they are aluminum if not galvanized but light.

Put a magnet on it. If its aluminum, it came from a very pricey above ground pool. Most are just sheet/galv metal.

fireflimoon · 2012-04-23, 10:57 PM

300ohm,

it's galvanized - did the magnet test. how much would it matter - would it be noticeable if swapped for aluminum?

Thanks

fireflimoon · 2012-04-23, 11:01 PM

ok just did the "test" on some aluminum flahing and IT is aluminum. will swap and see when I have a chance. Thanks 300ohm

300ohm · 2012-04-24, 12:36 AM

Quote:

would it be noticeable if swapped for aluminum?

Nope, just a bit lighter. You wont see any performance difference using galvanized or aluminum as the reflector that will move the meter.

mclapp · 2012-04-24, 10:28 PM

If the curve isn't the right shape it may not work any better than a flat reflector but still will work better than nothing. For channel 43 a 9 x 8 1/2" would be slightly better than a 9 1/2 x 9 but only a db or 2.

fireflimoon · 2012-04-25, 06:13 PM

Hi McLapp

Thanks...

I've cut 4 6" high by 40" wide aluminum flashing reflectors that are not "shaped" yet. Might try the angled reflector first since it seems easier. will center each piece behind a pair of whiskers to see...

Thanks

nezdepain · 2012-07-05, 07:51 AM

Hi mclapp
In your spreadsheet mentioned in the first page of this thread, there are performance results (theorical, practical?) for 6 bays. I have not seen plans on this forum for a "M6" or DB6. (the search tool on this forum does not allow 3-letters criteria). How is it made? Do you add one pair of bowties at the top and bottom of a DB4, with a crossover in the phase line to connect? Is the impedance still 300 ohms? Has anyone built one? Do you think it has a performance edge over a DB4, in practice, or it's not worth the extra effort? The 60 inches size of a DB6 is far more convenient for me, compared to a DB8 because of the clearance in my attic.
Thanks for your advice.

300ohm · 2012-07-05, 02:11 PM

Quote:

I have not seen plans on this forum for a "M6" or DB6. (the search tool on this forum does not allow 3-letters criteria). How is it made?

There was some playing around with 6 bays in Area 51 of this forum IIRC.
But the end result was little to no additional gain over a 4 bay. Antennas are stacked in 2, 4, 8, 16, 32 etc symmetrical configurations for the most gain for the space taken up.

If your attic space is limited, make 2 M4's or 2 SBGHs and couple them together with a quality splitter used in reverse. You will have to be careful about spacing, because you can produce straight ahead nulls in gain.

See the two antenna trick here : http://www.hdtvprimer.com/ANTENNAS/ganging.html

Xauto · 2012-07-05, 03:26 PM

You could make a 6bay but it would be feed of the the bottom, between each bay it should be crossed.

mclapp · 2012-07-13, 12:42 PM

The 6 bay showed decent gain on paper (computer models) but when I built it it really didn't work much better if any as compared to the 4 bays.

The one I modeled and built was fed in the center so there was an extra set of bowties on each side and an x over. I think things just start getting too far out of especially away from the resonant frequency. A better 6 bay may be to make (2) 3 bays and use a co phase line like the 8 bays use.

2012-04-23, 08:28 PM	#1158
BOUVAL Join Date: May 2011 Location: Vimont, Laval, Qc. Posts: 611	Fireflimoon, Before stacking, you should try a reflector with your m4, like some cardboard wrapped with alum foil 4~5 inches behind the M4. Have you tried a pre-amp. Is it for Rawdon or Pointe-Claire ? . __________________ Mes photos: http://s1140.photobucket.com/albums/n574/BOUVAL-OTA/

2012-07-05, 07:51 AM	#1167
nezdepain Join Date: Nov 2010 Location: Québec, QC Posts: 314	6-Bay Hi mclapp In your spreadsheet mentioned in the first page of this thread, there are performance results (theorical, practical?) for 6 bays. I have not seen plans on this forum for a "M6" or DB6. (the search tool on this forum does not allow 3-letters criteria). How is it made? Do you add one pair of bowties at the top and bottom of a DB4, with a crossover in the phase line to connect? Is the impedance still 300 ohms? Has anyone built one? Do you think it has a performance edge over a DB4, in practice, or it's not worth the extra effort? The 60 inches size of a DB6 is far more convenient for me, compared to a DB8 because of the clearance in my attic. Thanks for your advice.

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2012-04-22, 10:29 PM	#1156
mclapp Join Date: Aug 2008 Location: Upstate NY Posts: 597	For the reflector you can start out flat, if you need alittle more you can go to the curve or angled style for an improvement on UHF. Flat, angled, or curved will work the same on VHF-hi just make sure it's over 32 inches wide for Channel 13 but wider will be ok.

2012-04-23, 06:03 PM	#1157
fireflimoon Join Date: Nov 2011 Posts: 155	Thanks McLapp, (another question for you or anyone else who knows) If I wanted to vertically stack two m4's for ch 43 would the 9.5 x 9 be much better or worse than the other variants? I mean, how would the 9.5 x 9 compare to a m8 stack optimized for ch 43? Are we talking more than a couple db's or less than that? Thanks for the feedback...

2012-04-23, 10:15 PM	#1159
fireflimoon Join Date: Nov 2011 Posts: 155	Hi Bouval, It's for Rawdon but testing here first. I put 9 (4" inches apart) curved reflectors that came from an above ground pool that was brought down - pretty amazing how much aluminum you can find in that mess after you tear it down. So I an not sure how good they are as reflectors - but I am assuming they are aluminum if not galvanized but light. The rods are 46 inches long and curved. I slapped them on sloppy - not exactlt straight but just to test this evening. For some channels the reception was better than the gh4 in the attic - this one is on the second floor of the house. The curve comes from the fact that the "rods" were corner pieces of the pool and they acted as clamps somewhat for the vinyl of the pool at the top. Anyhow, it is for Rawdon. The thing about the M4 is that it can be stacked which isn't possible for Nikiml's GH designs which I really like. The channels that would be of interest are the Mount Mansfield channels and the PBS (VPT and Mountain Lake) but it is a stretch from there to Rawdon, so gain is important. I'm willing to give it a shot for ch 43 even though it has been mentioned that it is far. http://www.tvfool.com/?option=com_wr...7fcf06b2676ae0 Thanks

2012-04-23, 10:32 PM	#1160
fireflimoon Join Date: Nov 2011 Posts: 155	By the way, I know I am not using the optimum materials yet ...

2012-04-23, 10:57 PM	#1162
fireflimoon Join Date: Nov 2011 Posts: 155	300ohm, it's galvanized - did the magnet test. how much would it matter - would it be noticeable if swapped for aluminum? Thanks

2012-04-23, 11:01 PM	#1163
fireflimoon Join Date: Nov 2011 Posts: 155	ok just did the "test" on some aluminum flahing and IT is aluminum. will swap and see when I have a chance. Thanks 300ohm

2012-04-24, 10:28 PM	#1165
mclapp Join Date: Aug 2008 Location: Upstate NY Posts: 597	If the curve isn't the right shape it may not work any better than a flat reflector but still will work better than nothing. For channel 43 a 9 x 8 1/2" would be slightly better than a 9 1/2 x 9 but only a db or 2.

2012-04-25, 06:13 PM	#1166
fireflimoon Join Date: Nov 2011 Posts: 155	Hi McLapp Thanks... I've cut 4 6" high by 40" wide aluminum flashing reflectors that are not "shaped" yet. Might try the angled reflector first since it seems easier. will center each piece behind a pair of whiskers to see... Thanks

2012-07-05, 03:26 PM	#1169
Xauto Join Date: Sep 2008 Posts: 487	You could make a 6bay but it would be feed of the the bottom, between each bay it should be crossed.

2012-07-13, 12:42 PM	#1170
mclapp Join Date: Aug 2008 Location: Upstate NY Posts: 597	The 6 bay showed decent gain on paper (computer models) but when I built it it really didn't work much better if any as compared to the 4 bays. The one I modeled and built was fed in the center so there was an extra set of bowties on each side and an x over. I think things just start getting too far out of especially away from the resonant frequency. A better 6 bay may be to make (2) 3 bays and use a co phase line like the 8 bays use.