That one I wouldnt do. Instead I would increase its width to 32 to 44 or so inches to pick up vhf-hi.
That one I wouldnt do. Instead I would increase its width to 32 to 44 or so inches to pick up vhf-hi.RESIZE THE REFLECTOR GRID WIDTH:
The next thing that will need some adjustment is the width of the 24” wide reflector grid. The new CM4221HD reflector grid is 24” wide and the old CM4221 is only 20” wide. To do this, just carefully remove the plastic side retainers from all of those grid rods. Then cut exactly 2” off each of the aluminium grid rods and then reinstall the plastic side retainers.
I think thats going to depend on which channels.The old 4221 design was more multi-directional for those who desired to receive from various broadcast tower locations without the use of a rotor.
Channel 5 ?? You must have very strong vhf signals. Post your TVFool. The 4 bay bowtie doesnt really kick in with really good vhf-hi gain until the reflector width is above 28-32 inches or so.As far as VHF-Hi, I have found that the old CM4221 design was already pretty good at picking up analog channels VHF-5 through UHF-66. I suppose the new wider reflector design was intended to improve the VHF-Hi at the expense of losing some of the multi-directional qualities and the higher freqs above UHF-50.
Being plastic, what affect do these caps have on the V element? (I'm going to try it when I get home)‘V’ ELEMENT OBSTRUCTIONS:
There are some cute little 1” plastic covers that hide a portion of the elements at the connection points of each ‘V’ element on each bay. Remove these 8 cosmetic plastic caps and just toss them away, as they actually shorten the overall calculated length of each ‘V’ element by almost 2”.
I'll give this one a try too. How much of an Improvement do you see? If I remember correctly the bars go in towards the boom. I wonder what would happen if you flipped the bars over (or replaced them with something else) so the balun would move away from the boom?BALUN TO BOOM CLEARANCE:
The flat bars that the balun box is connected to are too close to the boom, so simply pull the balun assembly outwards and make sure that those flat bars are at least ½” away from the boom. I believe this may have just been an oversight that should have been mentioned within the antenna assembly instruction sheet.
[I believe this inward positioning of the balun was intended to accommodate the slim packaging dimensions and to reduce the risk of shipping damages]
Yep. Since you have the antennas in front of you, simply download 4nec2 for free and get busy, heh.Seeing a model of the modified antennas performance would assure us that this would work in other locations as well where a wider coverage area is desired.
Yes, some "Before" and "After" photos of this CM4221HD hardware modification would be nice.kooguy said:How about a picture showing the final modification?
Keep in mind the bowtie was invented in 1898 (and was re-invented 3 or 4 times since then, heh) and youre observing a very very old theory at work. Which is, when you reduce the forward gain of an antenna (by making the reflector smaller, for example) you increase the beamwidth of the radiation pattern. Which in the DTV age, can make aiming the antenna less critical and gives wider coverage. With digital, unlike analog, once youre comfortably past a certain threshold level, more gain can become irrelevant.The proof is not always proven by theory, but it is always proven by the tweeks of practical results.