i can't find anything more than what's on jogunn's site about tuning, no mention of altering the length at all for different frequencies, what is good for 26mhz is good for 29.5mhz with a tweak of the gamma according to the instructions,
I was wrong Bob, the tip is
NOT adjustable. Looking at the antenna image in the manual, it shows a screw is securing the tip element also. So, it looks like the whole antenna is fixed, and your right the frequency is adjustable via the gamma dog bone first at 43" from the top on the base element, then some fine tune adjustment can be made with the gamma stinger, but a caution says, "...do not reverse this process."
Boy, I understand now why guys have trouble with this antenna. They are using a pig tail stub connection, and that makes checking the SWR at the feed point impossible without a jumper or feed line, both of which can cause transformation if the load is not already near perfect at the desired frequency of operations. This says nothing about raising the antenna and seeing the match change due to height. This one might take a highwire act to tune.
You are right Bob, the JGSOG is intended to tune within the range given, 26.000 - 29.500 mhz, using the gamma adjustments only. So, in order to determine the length for this antenna for modeling purposes, one would have to get the specific length from JG and how it was measured. Or use a perfectly stock antenna from JG, assembled and measured between two specific points. We know for sure one point is the tip.
bob85 said:
i have see one guy claim his gunn is 28ft, the way i see it is its very likely 24ft+ of radiator which is a long 5/8wave @29mhz, the only way to know the length for sure is measure one that has not been messed with, then maybe model it on 29.5 and 26mhz,
You're right again, we need to know the antenna is unmodified, and where the bottom is measured from, just like you state.
bob85 said:
gamma fed scaffold poles about 3/4wave work but not nearly as good as a similar length sigma4 in the same mounting position,
everything i have read says that going longer than .64-5/8wave causes high angle lobes to form at the expense of low angle radiation, your 26ft model looks to be inline with what i have read,
So, this may mean the old 3/4 wave idea is still valid, right?
bob85 said:
i don't think there were any secrets in the base, if you read his later description its tripple walled tube, everything grounded like a sigma4 with the radials folded down,
I didn't think so either.
bob85 said:
we don't know how your buddy has his gunn set up, also take into account you don't see much difference between any two antennas in your area like some of us do,
I agree, but if you're right and this antenna is that much longer than a 5/8 wave of about 22.5' feet, then what about the 3/4 wave rule? My model doesn't seem to suggest that this particular radial design fixes the 3/4 issue like happens with the Sigma4. Maybe I'll have to fix the radials on my JG to fully horizontal, and see what the difference is.
bob85 said:
jogunn antennas look pretty well made, 6063-t6, not the best tube ever used in cb antennas as they claim, not even the second best but it looks and feels heavy duty compared to the vector 4000 tubing, several locals have bought vectors then bailed out when they assembled them and realized what 30ft of flacid aluminum looks & feels like.
My buddies SOG was mounted on a 25' foot tower and went through hurricane Ike, when it came thru the Houston area in 2008. It was bent a little, but still working. I took all of my stuff down.
