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isolation from mast
- Thread starter Splash1
- Start date
If your going to isolate the mast,it would make sense to ground your coax shield on the radio side of the choke so your antenna is still dc grounded.Seems to be the bit many people miss out when isolating masts and choking coax.
... And the other part they miss out on is that grounding the braid of that coax doesn't ground the antenna at all. Think about it.
Something else to think about. I've only heard of this isolating the mast thing in the last month or so. Wonder why it never seemed to crop up in the 40 some years I've been around radio before now? Have the ingredients used to make masts/antennas changed that much? Or has the means of test this stuff out really 'improved' that much. I kind'a doubt that last one, I haven't heard of any "hi-tech" testing being done on it. Or "low tech" testing for that matter. All I've heard/seen so far has been opinion, and there's nothing definite about that sort of testing, except to the one doing that testing.
Hmm, think I'd better quit at that point, it's very close to calling people 'politicians' and I wouldn't take that! Don't expect anyone else to either.
- 'Doc
-----------------
"Yes, we can! Yeah, but why should 'we'?"
Something else to think about. I've only heard of this isolating the mast thing in the last month or so. Wonder why it never seemed to crop up in the 40 some years I've been around radio before now? Have the ingredients used to make masts/antennas changed that much? Or has the means of test this stuff out really 'improved' that much. I kind'a doubt that last one, I haven't heard of any "hi-tech" testing being done on it. Or "low tech" testing for that matter. All I've heard/seen so far has been opinion, and there's nothing definite about that sort of testing, except to the one doing that testing.
Hmm, think I'd better quit at that point, it's very close to calling people 'politicians' and I wouldn't take that! Don't expect anyone else to either.
- 'Doc
-----------------
"Yes, we can! Yeah, but why should 'we'?"
I just lifted it from the pole and set it on the house roof, eventually I will get a large fiberglass rod and attach it to that on the pole and see if it affects the radiation pattern.
Well that is really strange, when I first got back into my antenna work recently, I had my Starduster model I call my Marconi 6 and my A99 on 20' foot mast and leaning up against my house and the roof affected both antennas so badly that I could tell with my receive and the tune was even affected. And you say your antenna got real quiet? Could it be that what you did affected the antenna so badly you just were not hearing well?
That is what I about to do add a FG rod and isolate the antenna. I bet if you get that thing well above your roof, it might still be quiet, but I'll bet it works a lot better than lying on the roof.
Hello George.
HiDef; said:
Yep HiDef, again I might agree, but IMO and depending on the magnitude of the currents, a choke, a sleeve, or radials alone will not effectively fix a CMC problem---on the order that I can really tell just by operating my radio or using the simple tools I have available. That is why I am taking this idea in baby steps with each feature trying to see if or how it affects tune and frequency, how the system load, an ultimately the RX/TX signals. It would also be nice if I could get some reliable feed back too. But if I can’t, I will just have to rely on the RX reports and depend on faith---that both TX and RX are reciprocal (meaning similar me thinks).
HiDef; said:
Well HiDef, I try to avoid thinking about the BS ideas on the internet. In fact if I can’t duplicate and idea pretty easily then I pay it little attention. Most of the time I think this is a simple misunderstanding though, and it has more to do with a lack in describing an idea and that lead to failure---so it is not always just BS either. I hear guys that I trust describing things, but sometimes I still fail to fully understand and apply the idea effectively. Other times I suspect that local conditions of soil, terrain, and ground clutter have a big affect as well on my effort to duplicate. In my testing I find that Mother Earth has a definite affect on a host of things I try to do, and when I raise my antenna I often see resonance and tune change. So within the range that I'm able to move---I don’t think I see the Earth being nullified and out of the picture like you suggest. Most of my antennas operate even at resonance with a bit of reactance, so I observe feedline transformation with the tune in most antennas I work with. And whenever I change the length of my feed line I see changes in match and resonance. If I was to speculate on this subject I would say just about everything I do has an affect on tune, match, and resonance---to say nothing about when I operate my radio and move in frequency away from true resonance. I tuned all my antennas at 27.205 and use the nice BW they provide to work my radio around in the CB band. I do all of my RX signal work on channel 39 lsb and then I naturally will be operating with a bit more of reactance. I have a method to my madness on this subject, but maybe for another time.
HiDef; said:
Yes again HiDef, but just imagine why designers choose to go with “plumbers delight” construction in antenna design. That was to increase reliability and strength and to eliminate the use of insulators where they could, and back in those days we probably did not have as good of plastic with good strength and isolation properties to fill that gap in reliable use.
HiDef; said:
I have a Wolf Radio 50_11M that is similar to the Ringo. It will tune just fine, but you have to tune in situ and as soon as you move the antenna the tune goes to hell in a hand basket. I tried adding the hub off of an A99 with four quarter wave radials to this antenna, but I could set the GPK only about 4” below the tuner and it was not an effective solution. Maybe if were able to get directly below within and inch maybe it would have responded differently. Have you had direct experience with the Ringo or is your claim here from HyGain advertising or anecdotal stories?
HiDef; said:
Can you give me a link to the thread you mention, I have not seen it. Maybe I’m even in a topic on this forum that I don’t visit often and got here via the new thread index. You are right about many posted claims on these forums, They are all over the board in a range of truth, BS, white lies, and out right lies, but most are probably just due to an inability to describe well what is observed.
HiDef; said:
Those are my sentiments about discussion and learning too. What I have done is certainly not scientific, in fact it is purely random observations and the process is completely evolving. I just record what I see regarding my Signal Reports and there are variables galore. I try to develop trends only that may suggest something to be considered in my thinking. In my past efforts I came at it from an approach of the typical CB Joe out there and what and how he might see things in working with his system. I discovered those guys for the most part just don’t care about the details since just about anything works and like I comment all the time in some threads:
“…we are just lucky the Mother Nature doesn’t require us to be perfect when operating our radios.”
Most of my recent stuff is posted here in my albums HiDef. You will see Antennas Work Sheets that a analyzer and inline meter Bandwidth scans as a result of tuning and modification efforts. They are not the helter-skelter type testing I do with my RX Signal Reports I mention above however.
I am planning right now to do some testing on my Sigma 4 with a coaxial choke, no choke, a ferret bead choke, and with isolation and without. I will for the most part be doing analyzer and SWR scans and recording the bandwidth curves before and after each iteration. I currently have my Sigma tuned pretty well regarding the Inline meter and SWR, but I have some reactance at resonance and I am going to attempt to tune a nice broad dip to true resonance resulting with a purely resistive match if I can. I will be scanning at the feed point with no feed line and if unsuccessful with the Sigma I will put my A99 up and do these test if I can get the tune note here on it. I spent some time making this attempt to tune with match and resonance at the same frequency in the middle of the CB band with my I-10K, but it is my opinion that the symmetry of that antenna is such to not allow a purely resistive match at resonance. I hopefully will be starting this week. I will keep you posted in a new album titled “Chokes and Isolation.”
Thought about it:headbang:headbang,are you trying to rewrite the laws of physics single handedly???????
You obviously don't comprehend the term (DC) ground.If you choke rf on the coax and isolate the mast on a dc grounded antenna you have broken the dc ground path,as the coax shield is also connected to the dc ground point on the antenna,when you ground the shield below the choke you have reestablished the dc ground but have still effectively choked common mode current.
But them maybe I'm wrong,which would also make W8JI wrong and others too,and you would then be the supreme antenna guru in the galaxy Doc.
A while back Moleculo posted W8JI's article on end fed/zepps,I suggest you read it,you may learn something from someone who understands antenna theory.
Hi Eddie,hows things mate?
jazzsinger,
If you have thought about it, I would have assumed that you would have realized that at best, you only grounded (AC or DC) half of a typical antenna, the half connected to the braid. What about the other half that isn't normally connected to the braid? Or thinking at it from another direction, you've only grounded half of that feed line, leaving the other half floating above ground.
So far, I can't think of any physics I've contradicted, nor W8JI, and I can assure you that I have absolutely no ambition to -ever- be "the supreme antenna guru in the galaxy"... it just doesn't pay enough, and how would you get all of that title onto a car tag or a door?
- 'Doc
If you have thought about it, I would have assumed that you would have realized that at best, you only grounded (AC or DC) half of a typical antenna, the half connected to the braid. What about the other half that isn't normally connected to the braid? Or thinking at it from another direction, you've only grounded half of that feed line, leaving the other half floating above ground.
So far, I can't think of any physics I've contradicted, nor W8JI, and I can assure you that I have absolutely no ambition to -ever- be "the supreme antenna guru in the galaxy"... it just doesn't pay enough, and how would you get all of that title onto a car tag or a door?
- 'Doc
Here's one for you. Everyone (even me) who posts stuff on the internet is wrong once in a while. Others more often.
Just google "W8JI wrong" for hours of entertainment.
Gawd that's a lot of typing.
The definition of resonance is no (or zero sum total) reactance. The IEEE definition of resonance is no reactance AND maximum current flow. Sounds like you have experience using an antenna analyzer that shows minimum SWR even with small amounts of reactance. That result would be from a radiation resistance other than 50 ohms and/or instrument error.
Hows about you build an isolated antenna with a knife switch to reconnect the radials to the mast. The knife switch could be actuated by something invisible to R.F. like string.
That way you can get instant A/B comparisons.
If you have access to an instrument with a log amplitude display you could make very precise SWR readings by measuring return loss. In theory the return loss will change if common mode currents propagate along the mast when it isn't isolated.
Keep in mind I'm saying isolation isn't necessary when resonant radials and a properly matched load have been established. If the antenna in question isn't tuned and matched properly all bets are off.
Either you have not seen the old Radio shack antennas I mentioned OR it was long ago and you have forgotten their construction. They already use plastic insulators quite effectively. It would not have been difficult to isolate the radials. The reason this was not done is it is unnecessary.
Here's one for you. Everyone (even me) who posts stuff on the internet is wrong once in a while. Others more often"
nobody is right all the time, so long as you keep moving forwards and learning thats what counts
"Just google "W8JI wrong" for hours of entertainment."
i have seen yuri cecil roy and tom argue about different topics, makes for interesting reading.
nobody is right all the time, so long as you keep moving forwards and learning thats what counts
"Just google "W8JI wrong" for hours of entertainment."
i have seen yuri cecil roy and tom argue about different topics, makes for interesting reading.
"Wonder why it never seemed to crop up in the 40 some years I've been around radio before now?"
some hams take their ticket to talk, they memorise answers to pass the test in order to be able to get on the air and talk,
they forget most of the little they had to memorise to pass,
they will more than likely talk to none techie folk steering well clear of the techie type because they aint interested in tech they are yappers tech is boring to them,
they talk about their aches and pains what they did yesterday after cutting the grass what they ate today and what they intend to eat tomorrow, they likely know all the local repeater frequencies and tones and have them in their radio or on a chart, yapper often sits hitting a button operating digimodes but not always, yapper may be a keen dxer chasing that rare dxcc that has eluded him, he knows guys that have it but cant figure out whey he is struggling to get it in the log, he wont ask techie because he dont want a hour lecture on radiation angles antenna petterns and propagation so he plugs away hoping one day he will get them all,
when yapper gets a problem with his station he will ask his yapper friends what could be wrong, between them they will come up with half a dozen things to try based on past experience using trial and error,
when yappers finals or some other fault develops on his radio its off to the dealers with it, yapper may know a local techie type that will check it out for him before they get backshafted at the dealers, only now does he really want to talk to the techie,
at rallies you will find yapper in the bar with a beer, in his bag of goodies he will have a half dozen new pl259's, a cheap 30w soldering iron some horrible lead free solder a cd with software for digimodes an icom world clock and maybe the latest dual band handie if the rally happens to be close to his birthday,
yapper has books by lou franklin in his collection,
others are interested in radio as opposed to yapping,
they memorise what they need to pass the test and see that as an introduction to radio, for them the real learning starts after they pass,
techie wants to understand radio and is more likely to seek out like minded techie folk who talk about radio as opposed to things in general, they may not always agree but they share a common passion, your gout, your daughters wedding what you ate for lunch or the accident you had last week in walmart carlot is of little interest to him, he tends to steer clear of repeaters prefering to work the birds or weedle out that qrp station on his newly built 4 square array or bobtail curtain, he is not baffled by terminated rhombics and magnetic loops.
he may be a dxer too, may even use digimodes but he will use his better understanding of radio to whip you in a contest,
when techie type has a problem with his station he has a gut instinct, his analytical mind gets him in the ballpark, he sees no reason to share his troubles with one and all looking for half a dozen ideas based on precision guesswork,
when a fault develops on his radio the last place hes taking it is the dealers, he will fix it himself,
he may or may not prefere the older radio with real components but if hes not too old and his eyes are good he will tackle even the smallest surface mount componenets and relish the challenge, old tube radios may arouse him,
at rallies techie type only visits the bar if hes genuinely thirsty, he has no time for banter with the guys from the local repeater groupe hes on the hunt for something interesting to play with, something in need of tlc, something he can convert to do what he wants it to do, those rare hv caps hes been needing for his project,
hes easy to spot his bag is full of things you have no idea about hes the guy ballancing the ex military antenna coupler on his shoulder, it looks nothing like your mfj but it has vacume variables and all silver plate inductors, you think you know what it is but you aint sure, is it a tuner or is it a marine bandpass filter from a ww2 battleship, it kinda looks like what you saw in ya mfj when you first bought it and had to take the lid off to add a few missing bolts and tighten everything up,
dont step on that mains cable hes trailing behind him on your way to the bar, its fastened to a hot air rework iron stuffed in his bag along with his russion triode and faulty grid dip meter complete with full set of coils,
with coupler ballanced on one shoulder and the old ft7b with leaky mixer fault in his other hand stepping on that trailing lead may pull the bag off his shoulder and the whole shebang could hit the ground, you will have his vacume relays pin diodes triacs and thyristors spilling everywhere, he will not be impressed with you,
techie has a well thumbed copy of maxwells reflections beside his bed, and a second copy in the bathroom.
some hams take their ticket to talk, they memorise answers to pass the test in order to be able to get on the air and talk,
they forget most of the little they had to memorise to pass,
they will more than likely talk to none techie folk steering well clear of the techie type because they aint interested in tech they are yappers tech is boring to them,
they talk about their aches and pains what they did yesterday after cutting the grass what they ate today and what they intend to eat tomorrow, they likely know all the local repeater frequencies and tones and have them in their radio or on a chart, yapper often sits hitting a button operating digimodes but not always, yapper may be a keen dxer chasing that rare dxcc that has eluded him, he knows guys that have it but cant figure out whey he is struggling to get it in the log, he wont ask techie because he dont want a hour lecture on radiation angles antenna petterns and propagation so he plugs away hoping one day he will get them all,
when yapper gets a problem with his station he will ask his yapper friends what could be wrong, between them they will come up with half a dozen things to try based on past experience using trial and error,
when yappers finals or some other fault develops on his radio its off to the dealers with it, yapper may know a local techie type that will check it out for him before they get backshafted at the dealers, only now does he really want to talk to the techie,
at rallies you will find yapper in the bar with a beer, in his bag of goodies he will have a half dozen new pl259's, a cheap 30w soldering iron some horrible lead free solder a cd with software for digimodes an icom world clock and maybe the latest dual band handie if the rally happens to be close to his birthday,
yapper has books by lou franklin in his collection,
others are interested in radio as opposed to yapping,
they memorise what they need to pass the test and see that as an introduction to radio, for them the real learning starts after they pass,
techie wants to understand radio and is more likely to seek out like minded techie folk who talk about radio as opposed to things in general, they may not always agree but they share a common passion, your gout, your daughters wedding what you ate for lunch or the accident you had last week in walmart carlot is of little interest to him, he tends to steer clear of repeaters prefering to work the birds or weedle out that qrp station on his newly built 4 square array or bobtail curtain, he is not baffled by terminated rhombics and magnetic loops.
he may be a dxer too, may even use digimodes but he will use his better understanding of radio to whip you in a contest,
when techie type has a problem with his station he has a gut instinct, his analytical mind gets him in the ballpark, he sees no reason to share his troubles with one and all looking for half a dozen ideas based on precision guesswork,
when a fault develops on his radio the last place hes taking it is the dealers, he will fix it himself,
he may or may not prefere the older radio with real components but if hes not too old and his eyes are good he will tackle even the smallest surface mount componenets and relish the challenge, old tube radios may arouse him,
at rallies techie type only visits the bar if hes genuinely thirsty, he has no time for banter with the guys from the local repeater groupe hes on the hunt for something interesting to play with, something in need of tlc, something he can convert to do what he wants it to do, those rare hv caps hes been needing for his project,
hes easy to spot his bag is full of things you have no idea about hes the guy ballancing the ex military antenna coupler on his shoulder, it looks nothing like your mfj but it has vacume variables and all silver plate inductors, you think you know what it is but you aint sure, is it a tuner or is it a marine bandpass filter from a ww2 battleship, it kinda looks like what you saw in ya mfj when you first bought it and had to take the lid off to add a few missing bolts and tighten everything up,
dont step on that mains cable hes trailing behind him on your way to the bar, its fastened to a hot air rework iron stuffed in his bag along with his russion triode and faulty grid dip meter complete with full set of coils,
with coupler ballanced on one shoulder and the old ft7b with leaky mixer fault in his other hand stepping on that trailing lead may pull the bag off his shoulder and the whole shebang could hit the ground, you will have his vacume relays pin diodes triacs and thyristors spilling everywhere, he will not be impressed with you,
techie has a well thumbed copy of maxwells reflections beside his bed, and a second copy in the bathroom.
- No one is chatting at the moment.
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