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RE: Modifying the FD-150 Factory Antenna
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by K0BG on June 26, 2009
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I have this really neat question to ask. How did you determine the resonant frequency? Did you use the lowest SWR? Or, did you do it correctly, and measure the input resistance when X equaled zero?
Remember too, the ground losses have a lot to do with the resonance point, and the resistive component. You just can't connect the antenna to the analyzer and expect the figures to be any where near close.
Lastly, if you do the same measurement with an average 2 meter HT ducky, you're in for a surprise.
Alan, KØBG
www.k0bg.com
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Modifying the FD-150 Factory Antenna
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by KA4DQJ on June 26, 2009
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I included a photograph with the article's submission. I don't know why it wasn't included in the article.
The results were checked using an active-circuit VHF field strength meter located 13 feet distant. Used on the ht, the modified antenna would move full meter scale against the unmodified antenna's less than 1/4 scale with the h/t locked into the same place for both tests. I should have put this in the article.
Some of the comments are astounding.
I didn't measure impedance of a rubber duckie on a "ground plane", or "hanging off a piece of coax". I measured it while attached to the chassis, the same conditions as actual use.
The "type acceptance" chatter I won't even address... someone needs to start their own thread. Ditto for the "real radio" stuff... it's a $45 radio that works, and has a one-year warranty; same as the "real" radios.
I didn't use "SWR". Please read and understand the article before commenting. Same advice for those wanting to know how I came by the "actual measured resonance", and "determine the resonant frequency". Someone may want to post an article about antenna bridges, what they do and how they work.
I'll pass on "drilling a hole" in the roof of the car to either test or use the antenna.
"X equals zero"? I'm not working with HF frequencies here. The broad frequency response of VHF antennas, and especially lossy antennas such as h/t duckies is such that X isn't a consideration. At VHF frequences ballpark is perfectly fine. In fact, it's hard enough to determine just where the null is occuring on a VHF duckie antenna... it is so broad.
And, no "surprise" here when measuring duckies on an analyzer... I routinely do it when I need to distinguish between a scanner, business band and 2m duckies when searching my collection. The 2m duckies will always be resonant in the 2m band presuming that they are well made for the 144-148mhz range.
Last, it would suit me fine if eham just took this article down. In any case I won't be writing another. If you think the modification will improve your FDC-150 peformance, then go for it. If not, then you're free to forget it. Since it's not a "real radio" anyway, you won't be out anything.
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Modifying the FD-150 Factory Antenna
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by KE7AKS on June 26, 2009
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In the good ol' DAZE we just used a FIELD STRENGTH METER like the one that is a SWR-FIELD STRENGTH METER.
Establish a fixed distance where youget mid scale Field Strength while transmitting. Try the additional wire and see if the strength gets better. Then try transmitting on a higher frequency and if it gets better, then the antenna is still too short...
The real proof of an antenna is - how does it really function, not in some other measurement.
It was a GREAT ARTICLE.
I was thinking of writing an article on using a 3 way light switch to switch from POWER SUPPLY power to 12V. BATTERY power, but I figured the GRAMMAR VOLTURES would have too much fun with it. Not to mention the techie types, not wanting an over simplified solution like that.
I want more helpfull hints like this ---
73
KE7AKS
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RE: Modifying the FD-150 Factory Antenna
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by K7DAA on June 26, 2009
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Thomas:
I feel your pain regarding all of the idiot comments--this is precisely the reason you won't find people like myself writing articles for eHam or QRZ. Just too many "experts" who have to chime in with their "brilliant" commentary.
I've read a quite a number of articles submitted by well-meaning people like yourself, hoping to share a bit of information and advance the hobby, who end up being discouraged by ever doing such a thing again because of the rudeness and even personal attacks by hams in our on-line community. Some people even complain that they get personal threats via email after posting!
Such a shame--and to those of you that seem to feel that your day is not complete unless you've added your two cents, or put down someone or their ideas online--shame on you! You are not helping the hobby one bit! You are driving people away and dissuading folks from participating in what could be very meaningful and useful discourse because of your need to spout off!
Guys, could you please, every once in a while, just say something like, "Hey, thanks for taking the time to write this article!", and just leave it at that? Would it kill some of you to just be kind to each other and encourage honest, open discussion?
Remember what mom said: "If you can't think of anything nice to say about someone, don't say anything at all"
Anyway, thanks Thomas, at least some of us appreciate the effort you put in to this.
73,
Dave - K7DAA
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RE: Modifying the FD-150 Factory Antenna
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by K8QV on June 26, 2009
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"I included a photograph with the article's submission. I don't know why it wasn't included in the article.
The results were checked using an active-circuit VHF field strength meter located 13 feet distant. Used on the ht, the modified antenna would move full meter scale against the unmodified antenna's less than 1/4 scale with the h/t locked into the same place for both tests. I should have put this in the article.
Some of the comments are astounding.
I didn't measure impedance of a rubber duckie on a "ground plane", or "hanging off a piece of coax". I measured it while attached to the chassis, the same conditions as actual use.
The "type acceptance" chatter I won't even address... someone needs to start their own thread. Ditto for the "real radio" stuff... it's a $45 radio that works, and has a one-year warranty; same as the "real" radios.
I didn't use "SWR". Please read and understand the article before commenting. Same advice for those wanting to know how I came by the "actual measured resonance", and "determine the resonant frequency". Someone may want to post an article about antenna bridges, what they do and how they work.
I'll pass on "drilling a hole" in the roof of the car to either test or use the antenna.
"X equals zero"? I'm not working with HF frequencies here. The broad frequency response of VHF antennas, and especially lossy antennas such as h/t duckies is such that X isn't a consideration. At VHF frequences ballpark is perfectly fine. In fact, it's hard enough to determine just where the null is occuring on a VHF duckie antenna... it is so broad.
And, no "surprise" here when measuring duckies on an analyzer... I routinely do it when I need to distinguish between a scanner, business band and 2m duckies when searching my collection. The 2m duckies will always be resonant in the 2m band presuming that they are well made for the 144-148mhz range.
Last, it would suit me fine if eham just took this article down. In any case I won't be writing another. If you think the modification will improve your FDC-150 peformance, then go for it. If not, then you're free to forget it. Since it's not a "real radio" anyway, you won't be out anything."
Well said. Thanks for trying, but this is a place where everybody already knows everything.
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RE: Modifying the FD-150 Factory Antenna
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by AH6RR on June 26, 2009
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I always say a expert = ex as in Has been and spert as in drip under pressure. Or if you cant dazzle them with brillance baffle them with BS.
Come on it's a cheap peice of Chinese hardware if it blows up it only $50 not $350 Jappanese Radio.
73
AH6RR
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RE: Modifying the FD-150 Factory Antenna
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by K8MMG on June 26, 2009
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Thanks for the article. You've got to have a thick skin when you write something and post in on the internet. Keep 'em coming. Regarding the radio: I've spent mucho dinero on some "big name" HTs and can easily say that this rock-solid import has out-performed them (no, not kidding). It is built like a tank and just works. Oh and it comes with a MARS mod already done! It may not come with all the fancy bells and whistles but you can't beat it for the price.
73,
Brandon
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RE: Modifying the FD-150 Factory Antenna
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by ALCO141 on June 27, 2009
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hey,
i thank you for writing this article, more than some of the hypercritical folks seem to do most of the time, i like these articles, they are low tech, can be done by most folks, dont require a lot of equipment, forget the monday morning quarterbacks. if they have something constructive to say then say it, otherwise like your mama told you if you dont have anything nice to say then....shut the ... up. maybe for those of us that are new here a constructive explanation of how to measure with what equipment may have been more insightfull than... did you hang the wire off a telephone pole at midnight in the quarter moon during the spring equinox, as we all know this is the only true way to measure the angle of the dangle... of the antenna that is.
as far as the chinese HT, i dont have one, but since when are hams gear snobs? oh you have one of thooose radios? most guys that i know like the simple, cheap, functional gear method of operating.
alex
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Modifying the FD-150 Factory Antenna
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by KC8PCL on June 27, 2009
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It never ceases to amaze me, The amount of so called illegal radio's that arrive in this country. If they are in fact illegal, Why is the import of these radios not monitored and enforced? The radio's are here now. What is the point of saying they are illegal? If you have one, Use it. As for improvements, keep them coming. Don't be put off by some that feel they need to point out their knowledge of the law. This is a FUN hobby, Enjoy it. If you can't say anything positive, Keep your posts to yourself. There is enough negativity in the world today. Why add to it, Just saying. 73, and keep posting. I for one enjoy reading things like this.
KC8PCL
Dave
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RE: Modifying the FD-150 Factory Antenna
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by K4RAF on June 27, 2009
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It is easier to beg forgiveness than ask for permission.
If you do it, keep it to yourself...
Today's hams only want to argue legality, not technical merits...
Raf
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