Ok some of your antenna dudes I need to know the lengths that a pdl2 would need to be shortened for use on ten with say 28.500 being center also the wires on the outside and I don't have a tuner so that is not an option!!
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PDL2 for ten need some lengths
- Thread starter yama junk owna
- Start date
Probably the simplest method of rebuilding the antenna would be to measure the lengths of the elements used now, and find the antenna's resonant frequency as close as you can get it. Then, for each elelment, multiply the length by the resonant frequency. That number is what you'd use to find the 'new' length for the 'new' resonant frequency. Divide the 'new' number by the 'new' frequency and you have a very close 'guess' to the proper length. Since you're going higher that the original resonant frequency, subtract the 'new' length from the 'old' length and you have how much you should shorten the element.
There's never an 'exact' figure for those lengths. They always vary to some extent by where the antenna is mounted, what's around it and 'ya-da', 'ya-da', 'ya-da'. So there's always some trimming that goes with tuning an antenna unless you are very, very, lucky. That's the reason for the "guess" about finding the 'new' lengths. And with any kind of 'guess' it's better to have just a little bit 'more' than 'not enough', so an inch or two 'extra' for the driven element, which you can trim off later, is a pretty good idea. Director elements are always shorter than the driven one, so a slight 'fudge' in that direction is 'allowed'. Reflectors are slightly longer than the driven one, so a 'fudge' in the 'other' direction is nice. Directors and reflectors are not ~that~ critical, so don't need to be as 'exact' as the driven element.
Have fun.
- 'Doc
PS - Nothing new at all in the above, just a different way of saying it. If I missed anything else you already knew, let me know and I'll add it
There's never an 'exact' figure for those lengths. They always vary to some extent by where the antenna is mounted, what's around it and 'ya-da', 'ya-da', 'ya-da'. So there's always some trimming that goes with tuning an antenna unless you are very, very, lucky. That's the reason for the "guess" about finding the 'new' lengths. And with any kind of 'guess' it's better to have just a little bit 'more' than 'not enough', so an inch or two 'extra' for the driven element, which you can trim off later, is a pretty good idea. Director elements are always shorter than the driven one, so a slight 'fudge' in that direction is 'allowed'. Reflectors are slightly longer than the driven one, so a 'fudge' in the 'other' direction is nice. Directors and reflectors are not ~that~ critical, so don't need to be as 'exact' as the driven element.
Have fun.
- 'Doc
PS - Nothing new at all in the above, just a different way of saying it. If I missed anything else you already knew, let me know and I'll add it
Frequency scalling is a simple ratio. If the antenna is resonant now on 27.185 then take 27.185 and divide it by the new freq 28.500 and multiply the result by the present measurements to get the new measurements.It works out to all the new measurements should be about 95.4 % of what they are now.Like Doc said,it will get you close enough to start fine tuning but nothing may be 100% accurate depending on the surroundings.
pdl
Doc hit the nail on the head,I did the same thing a few years ago for a fellow that wanted down on 26.500 I used a mfj 259b to find out were it was resonanting at and just cut the new wires longer,hooked the 259b back up, had to do some trimming and had him on the air in less than an hour.I think he is still using that durn thing
Doc hit the nail on the head,I did the same thing a few years ago for a fellow that wanted down on 26.500 I used a mfj 259b to find out were it was resonanting at and just cut the new wires longer,hooked the 259b back up, had to do some trimming and had him on the air in less than an hour.I think he is still using that durn thing
Re: pdl
And so I understand you correctly, you used LONGER wires to get him below 26.5 and trimmed them until you saw a good match. Right? Did you extend the fiberglass rods out to take up the larger wire?
What about the gamma match, did you adjust that at all? If not, then the wire elements are probably less than optimum.smokercraft said:
And so I understand you correctly, you used LONGER wires to get him below 26.5 and trimmed them until you saw a good match. Right? Did you extend the fiberglass rods out to take up the larger wire?
pdl
Masterchief, I don't like to type so I just gave the short version.Yes we did take out the elements some what.I don't remember just how much anymore, it has been a few years but I think my old brain probably could still figure it.We did adjust the gammas alittle but I don't think it was much either.I am not a antenna expert, Just a old guy that likes to play when the weather gets warm.I have rebuilt a few pdl"s couple of moonraker's but my favorite has to be the old hygain big gun two,now that was a quad if you can keep the big thing in the air Oh by the way I really like your idea about the blind rivets,If I get the chance to rebuild something else I will give them a try.
Masterchief, I don't like to type so I just gave the short version.Yes we did take out the elements some what.I don't remember just how much anymore, it has been a few years but I think my old brain probably could still figure it.We did adjust the gammas alittle but I don't think it was much either.I am not a antenna expert, Just a old guy that likes to play when the weather gets warm.I have rebuilt a few pdl"s couple of moonraker's but my favorite has to be the old hygain big gun two,now that was a quad if you can keep the big thing in the air
Oh by the way I really like your idea about the blind rivets,If I get the chance to rebuild something else I will give them a try.
Re: pdl
Oh thank GOD! When scaling antennas, you have to do the whole package! Good job Smokey!smokercraft said:
:shock: i guess it's just me, i just can't see doing it to a pdl-ll i would buy another antenna. it's a classic that can't be replaced.
rfoverlord said:
Not planning on cutting anything other than the wires so how is that going to hurt the pdl ? The other parts will adjust. beside it's better to use the old classics than to stick them in a box on a shelf.
true dat! i didn't think it would sit on a shelf, and i suppose if your not cuttin it all up then all is wel(as if i had any say..LOL)At least it's being used and it's an educational project with great rewards. good luck with it.
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