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Broadband HT antenna?
Does anyone make a telescoping HT antenna meant to operate (1/4 wave)
over a broad band of frequencies with marking for those frequencies? Most HT's can be modified to operate outside the amateur bands, like on GMRS, MURS, FRS, etc. But I don't like doing this without a proper antenna. It would be simple enough to make a 1/4 wave telescoping antenna with calibration marks for everything VHF and UHF, just extend it to the right length. It would have an easy way to set it to the right length. Does anyone make an antenna like this? TNX, Bruce AF8F |
Bruce W.1 wrote:
Does anyone make a telescoping HT antenna meant to operate (1/4 wave) over a broad band of frequencies with marking for those frequencies? I think I saw one that was advertised as 1/4 wave on 70cm when closed, 1/4 wave on 2m when fully extended. Can't remember the brand, or where I saw it, though. -j |
In article ,
Bruce W.1 wrote: Does anyone make a telescoping HT antenna meant to operate (1/4 wave) over a broad band of frequencies with marking for those frequencies? I've seen one or two such on a dealer's table at a local hamfest, although I'm not sure that they come pre-marked - the package gave instructions for the number of segments to collapse to achieve resonance on 220 and 440. I think one was made by ADI and/or Premier but I can't be sure. Most HT's can be modified to operate outside the amateur bands, like on GMRS, MURS, FRS, etc. But I don't like doing this without a proper antenna. You really shouldn't do it (well, at least, not transmit) even _with_ a proper antenna. Very few, if any amateur-radio HTs are certificated for transmission on those bands, and using an "opened-up" ham HT to transmit (even if you have a suitable GMRS license) is a rules violation which could cost you your amateur ticket. FRS and GMRS have very strict technical rules about the frequency accuracy of their oscillators due to the tight inter-channel spacings, and it's likely that at least some ham HTs are too sloppy in design (or too poorly calibrated) to hit the frequencies accurately. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
On Tue, 05 Apr 2005 10:38:47 -0500, Joe User
wrote: Bruce W.1 wrote: Does anyone make a telescoping HT antenna meant to operate (1/4 wave) over a broad band of frequencies with marking for those frequencies? I think I saw one that was advertised as 1/4 wave on 70cm when closed, 1/4 wave on 2m when fully extended. Can't remember the brand, or where I saw it, though. -j Radio Shack sells one. I have one, but I wouldn't want to hang it on an HT connector. Too heavy. I use it on a Bearcat scanner. http://www.radioshack.com/product.as...ct%5Fid=20-161 Dick - W6CCD |
"Dick" LeadWinger wrote in message
... On Tue, 05 Apr 2005 10:38:47 -0500, Joe User wrote: Bruce W.1 wrote: Does anyone make a telescoping HT antenna meant to operate (1/4 wave) over a broad band of frequencies with marking for those frequencies? I think I saw one that was advertised as 1/4 wave on 70cm when closed, 1/4 wave on 2m when fully extended. Can't remember the brand, or where I saw it, though. -j Radio Shack sells one. I have one, but I wouldn't want to hang it on an HT connector. Too heavy. I use it on a Bearcat scanner. http://www.radioshack.com/product.as...ct%5Fid=20-161 Dick - W6CCD I can agree with Dick... I have 2 such Radio Shack antennas. I use one for my Service Monitor, the other is for any other test purpose I may have, NOT for replacement for an H.T. A tad too heavy. They were heavy for like the HTX 202, if you used it on one of the micro radios out now days, the thing would be top heavy. cl |
I agree. You run into the same problems that Public Safety radios
have to deal with. That is, trying to operate over a wide range perhaps 150 -174 MHz with a high power radio. Certainly the 1/4 wave is the best you can do to avoid shutdown of the radio. For Dual-band 2m/440 operation and in particular when operating MARS, a 1/4 wave 144 MHz antenna will provide a more satisfactory load at UHF as well, although with a compromised pattern on those frequencies. One of the most frightening tests I performed with 2m/440 ham antennas was that they were extremely sharp in bandwidth and resulted in extreme SWR beyond -+ 2-3 MHz on either band. Public safety personnel often don't understand how hams can have high performance dual band antennas and they can't. Some suspiciously consider a conspiracy. The simple answer lies in the frequency coordination of the repeater frequencies on both bands, and the narrow but coincidental sliver of frequencies we use for mobile operation. If you have a telescopic whip you are blessed. Carry a tape measure and chart with you. Of course there are other issues regarding MURS, GMRS and FRS that are completely awkward and you might as well carry a real FRS radio along with a Commercial radio with a bank devoted to the ham bands on your bat-belt. I contest the mentality that says you should "open up" a ham radio for "emergency use only" because you compromise the emergency situation by not using a radio up to the task. You can use a "church-key" as a can opener, but if you are truly serious you will pack a can opener. Jim, ac6tk "Dave Platt" wrote in message ... In article , Bruce W.1 wrote: Does anyone make a telescoping HT antenna meant to operate (1/4 wave) over a broad band of frequencies with marking for those frequencies? I've seen one or two such on a dealer's table at a local hamfest, although I'm not sure that they come pre-marked - the package gave instructions for the number of segments to collapse to achieve resonance on 220 and 440. I think one was made by ADI and/or Premier but I can't be sure. Most HT's can be modified to operate outside the amateur bands, like on GMRS, MURS, FRS, etc. But I don't like doing this without a proper antenna. You really shouldn't do it (well, at least, not transmit) even _with_ a proper antenna. Very few, if any amateur-radio HTs are certificated for transmission on those bands, and using an "opened-up" ham HT to transmit (even if you have a suitable GMRS license) is a rules violation which could cost you your amateur ticket. FRS and GMRS have very strict technical rules about the frequency accuracy of their oscillators due to the tight inter-channel spacings, and it's likely that at least some ham HTs are too sloppy in design (or too poorly calibrated) to hit the frequencies accurately. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
I for one take the easy way out on all bands, vhf hf etc.
Use "tuners". At least your protecting whatever rigs ouput you have. It does'nt speak to efficiency that way, but I get rather good results with my G6 VHF antenna on all modes and on MARS freqcys also which are out of the HAM band limits. HF same thing. MFJ diferential T tuner with roller coil gets me anywhere I want to go from 3.5 mhz on down to 30 mhz. Kokomo Joe ************************************************** ** * Ham KH6JF AARS/MARS ABM6JF QCWA WW2 VET WD RADIO * * Army MARS State Coordinator for Hawaii * ************************************************** ** On Tue, 5 Apr 2005, JB wrote: I agree. You run into the same problems that Public Safety radios have to deal with. That is, trying to operate over a wide range perhaps 150 -174 MHz with a high power radio. Certainly the 1/4 wave is the best you can do to avoid shutdown of the radio. For Dual-band 2m/440 operation and in particular when operating MARS, a 1/4 wave 144 MHz antenna will provide a more satisfactory load at UHF as well, although with a compromised pattern on those frequencies. One of the most frightening tests I performed with 2m/440 ham antennas was that they were extremely sharp in bandwidth and resulted in extreme SWR beyond -+ 2-3 MHz on either band. Public safety personnel often don't understand how hams can have high performance dual band antennas and they can't. Some suspiciously consider a conspiracy. The simple answer lies in the frequency coordination of the repeater frequencies on both bands, and the narrow but coincidental sliver of frequencies we use for mobile operation. If you have a telescopic whip you are blessed. Carry a tape measure and chart with you. Of course there are other issues regarding MURS, GMRS and FRS that are completely awkward and you might as well carry a real FRS radio along with a Commercial radio with a bank devoted to the ham bands on your bat-belt. I contest the mentality that says you should "open up" a ham radio for "emergency use only" because you compromise the emergency situation by not using a radio up to the task. You can use a "church-key" as a can opener, but if you are truly serious you will pack a can opener. Jim, ac6tk "Dave Platt" wrote in message ... In article , Bruce W.1 wrote: Does anyone make a telescoping HT antenna meant to operate (1/4 wave) over a broad band of frequencies with marking for those frequencies? I've seen one or two such on a dealer's table at a local hamfest, although I'm not sure that they come pre-marked - the package gave instructions for the number of segments to collapse to achieve resonance on 220 and 440. I think one was made by ADI and/or Premier but I can't be sure. Most HT's can be modified to operate outside the amateur bands, like on GMRS, MURS, FRS, etc. But I don't like doing this without a proper antenna. You really shouldn't do it (well, at least, not transmit) even _with_ a proper antenna. Very few, if any amateur-radio HTs are certificated for transmission on those bands, and using an "opened-up" ham HT to transmit (even if you have a suitable GMRS license) is a rules violation which could cost you your amateur ticket. FRS and GMRS have very strict technical rules about the frequency accuracy of their oscillators due to the tight inter-channel spacings, and it's likely that at least some ham HTs are too sloppy in design (or too poorly calibrated) to hit the frequencies accurately. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
On Tue, 05 Apr 2005 05:48:12 GMT, "Bruce W.1" wrote:
Does anyone make a telescoping HT antenna meant to operate (1/4 wave) over a broad band of frequencies with marking for those frequencies? Most HT's can be modified to operate outside the amateur bands, like on GMRS, MURS, FRS, etc. But I don't like doing this without a proper antenna. It would be simple enough to make a 1/4 wave telescoping antenna with calibration marks for everything VHF and UHF, just extend it to the right length. It would have an easy way to set it to the right length. Does anyone make an antenna like this? TNX, Bruce AF8F Why don't you get your own telescoping whip, attach it to a connector for your radio, and using the formulas for frequency and antenna lengh, mark the whip yourself? The only question is whether your handi talkie input isn't already pre-configured strictly for the helio-wound rubber duckie that comes with it. For example, the rubber duckie that comes with my 2 meter Icom T2-H, at 147 Mhz, has an swr of 3.0, and an impedance of just under 400 ohms, according to my MFJ 269 antenna analyzer. But the antenna works fine on the handie talkie. bob k5qwg bob k5qwg |
In article ,
Bob Miller wrote: For example, the rubber duckie that comes with my 2 meter Icom T2-H, at 147 Mhz, has an swr of 3.0, and an impedance of just under 400 ohms, according to my MFJ 269 antenna analyzer. But the antenna works fine on the handie talkie. You might want to try repeating the measurement with the MFJ 259 held up beside your head as if it were an HT. I've been told that HT duck antennas are often tweaked for best match and lowest SWR when used in this position, with a significant amount of capacitive coupling to the user's head. Measurements of a couple of 'em with my 269 seemed to support this - they "read" a lot better in a "typical HT use" position than they do if the analyzer is being held out at arm's length. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Dave Platt wrote:
In article , Bob Miller wrote: For example, the rubber duckie that comes with my 2 meter Icom T2-H, at 147 Mhz, has an swr of 3.0, and an impedance of just under 400 ohms, according to my MFJ 269 antenna analyzer. But the antenna works fine on the handie talkie. You might want to try repeating the measurement with the MFJ 259 held up beside your head as if it were an HT. I've been told that HT duck antennas are often tweaked for best match and lowest SWR when used in this position, with a significant amount of capacitive coupling to the user's head. Measurements of a couple of 'em with my 269 seemed to support this - they "read" a lot better in a "typical HT use" position than they do if the analyzer is being held out at arm's length. ================================================== ====== That's the part that's difficult to measure. Some of my good HT antennas that came with the radio, when tested alone on a good ground plane, have lousy SWR. Yet these radios are fully capable of being connected to an external antenna. A perfect quarter wave is 36 ohms. Yet HT's are happy driving an external 50 ohm antenna. I do have a few telescoping antennas. This might be the best solution. I was hoping someone made one built like a tape measure. A tiny SWR meter that mounted between the HT and antenna would be a nice solution. I'll admit I like to have the ability to at least jump over to the FRS or the GMRS. |
In article ,
Bruce W.1 wrote: That's the part that's difficult to measure. Some of my good HT antennas that came with the radio, when tested alone on a good ground plane, have lousy SWR. Yet these radios are fully capable of being connected to an external antenna. A perfect quarter wave is 36 ohms. Yet HT's are happy driving an external 50 ohm antenna. Well, for one thing, the transmitter "sees" the total load - the quarterwave's radiation resistance, the radiation resistance of whatever is servicing as the ground plane / counterpoise / other half of the dipole, and the losses of both. The role of GP/counterpoise is usually taken by a combination of the HT's metal body, and the user's skin (capacitively coupled to the HT body). The radiation resistance and losses of the HT body and user's skin are difficult to predict, and no doubt vary all over the place depending on the situation, sweat levels, phase of moon, etc., but I imagine they're high enough to boost the total feedpoint impedance up well above 36 ohms. For another things, HT finals _have_ to be reasonably tolerant of poor matches, or the failure rate would be astronomical - there's just too much variation in antenna feedpoint impedance to allow such devices to be designed with finicky, sensitive finals. I would guess that modern HTs all use internally-ballasted multiple-emitter RF transistors which are very conservatively rated (e.g. voltage breakdown ratings of several times higher than the power supply voltage, plenty of excess current-dissipation margin due to the ballasting) and may include automatic high-SWR power foldback circuitry as well. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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