Re: [RCSE] 555 antenna length
One way to make the antenna a little longer is to add a wider bit at the top, say a copper coin, or something like that. It will also receive a wider spectrum ... Having a very overlong antenna will improve reception, as ham radio guys know, as long as it isn't totally out of phase. Ham guys sometimes use antennas 20 times longer than the usual 1/4 or 1/2 wave, with good effect! Very long antennas tend to be very directive, though! Transmitting is another matter, but widening the top of the antenna widens it's possible transmitting spectrum. Yours, Tord RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
Hi All We in South Africa are having a great deal of success extending the antenna on our 35Mhz JR / Graupner receivers. Having performed the calculation below, I come up with a quarter wavelength of 2,141M. Would this explain why extending our antenna works so well? Does anyone else have similar exerience? Our theory was that we where compensating for the blancking (faradays cage) effect of carbon in our fuselages. Regards Mark -- Original Message --- From: Soaring@airage.com (Soaring) To: Soaring@airage.com Sent: Wed, 26 Jan 2005 06:21:43 -0500 Subject: Soaring V1 #5035 David, If you're fussy, the correct antenna length depends upon the frequency. Wavelength = Speed of Light / frequency In meters = 299, 792.458 / frequency in MHz In inches = 11,802,852.6771654 / frequency in MHz Quarter Wave = Wavelength / 4 R/C receiver antenna are typically quarter wave, so compute the wave length using a formula above and then divide by 4. For example 72.000 MHz frequency band generically, ignoring decimal 1/4 Wave = 1.0409 meter (1040.9 mm) 1/4 Wave = 40.982 inch 72.270 MHz frequency, specifically 1/4 Wave = 1.0370 meter (1037.0 mm) 1/4 Wave = 40.829 inch Higher the frequency, shorter the antenna. Note that the computed lengths are total, not just the portion sticking out of the receiver case. Total length will include any wire inside the case plus the length of trace on the PC board. Regards, Tim RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
The mentioned theories are good. But our RX's don't use resonant antennas so the tuning of the antenna doesn't really matter too much. Use ~41 inches and you'll be fine. Bill Swingle RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
A totally non-resonant antenna would transfer 0 power and you would receive absolutly nothing. -charles On Wed, 26 Jan 2005, Bill Swingle wrote: The mentioned theories are good. But our RX's don't use resonant antennas so the tuning of the antenna doesn't really matter too much. Use ~41 inches and you'll be fine. Bill Swingle RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
On Wed, Jan 26, 2005 at 01:33:29AM -0600, Tim Engel wrote: | If you're fussy, the correct antenna length depends upon the frequency. | | Wavelength = Speed of Light / frequency | In meters = 299, 792.458 / frequency in MHz | In inches = 11,802,852.6771654 / frequency in MHz The problem here is that the speed of light is slightly lower in the antenna, which is usually described with a `velocity factor' or a longer `electrical length'. | Quarter Wave = Wavelength / 4 | R/C receiver antenna are typically quarter wave, so compute the wave length | using a formula above and then divide by 4. | | For example | 72.000 MHz frequency band generically, ignoring decimal | 1/4 Wave = 1.0409 meter (1040.9 mm) | 1/4 Wave = 40.982 inch The standard formula for a 1/4 wave wire antenna, taking into account the velocity factor is (234 / frequency) in feet. So for 72.00 mHz the answer would be 3.25 feet or 39 inches rather than 41 inches. | Note that the computed lengths are total, not just the portion | sticking out of the receiver case. Total length will include any | wire inside the case plus the length of trace on the PC board. It actually gets more complicated than that. There may be some sort of matching network (usually a loading coil or a capacitator) in the receiver, which will require an antenna that's shorter (or longer) than the value calculated to be used. For 72 mHz, the calculated length is right about one meter, and that's how long most of the antennas are, so 39 inches is probably very close to what the antenna ought to be, but to be sure, I'd just duplicate the original antenna length. For 75 mHz, the antenna would be even shorter. I imagine that the manufacturers may actually use stock 72 mHz antennas and then adjust it so it's resonant. Or they may not worry about it being resonant at all -- after all, how often do you drive an R/C car a mile away? For other frequencies (40 mHz, 35 mHz, 27 mHz, etc.) the antennas are still usually about a meter long, so there's almost certainly a loading coil of some sort in the receiver. To figure out the correct length, you'd need to measure the loading coil -- it would probably just be easier to duplicate the original antenna. And yes, R/C antennas usually *are* resonant antennas, though they're usually tuned pretty sloppily. There is certainly room to tune them better, but unless you know what you're doing, I'd suggest not adjusting the length of your R/C antennas. Repairing antennas is easy enough -- just make it the same length -- but making them longer or shorter is a great way to reduce your range unless you open up the receiver and see components the antenna is connected to. -- Doug McLaren, [EMAIL PROTECTED] A flashlight is a case for holding dead batteries. RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
Alright. SLOPPY Resonant. SIMON, help me out here. The bottom line remains. Make the wire between 39 and 41 inches, plus or minus an inch or two, and you'll be fine. It really won't matter. I've used wires of ~24 to 50 inches and they worked fine. SLOPPY indeed. By far the more important factor is the specific installation and layout of the wire. Straight and unshielded is the rule. Bill Swingle RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
You don't need my help :^) An non resonant antenna length of 39 will work on all RX's operating @ 72MHz. A couple of inches either way? I know I don't have the equipment here at work sensitive enough (our SA's, NA's, FC's, are only around $45,000 ea) to measure such a small change (dBm) in sensitivity... Quoting Bill Swingle [EMAIL PROTECTED]: Alright. SLOPPY Resonant. SIMON, help me out here. The bottom line remains. Make the wire between 39 and 41 inches, plus or minus an inch or two, and you'll be fine. It really won't matter. I've used wires of ~24 to 50 inches and they worked fine. SLOPPY indeed. By far the more important factor is the specific installation and layout of the wire. Straight and unshielded is the rule. Bill Swingle RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
If you're fussy, the correct antenna length depends upon the frequency. Wavelength = Speed of Light / frequency In meters = 299, 792.458 / frequency in MHz In inches = 11,802,852.6771654 / frequency in MHz Quarter Wave = Wavelength / 4 R/C receiver antenna are typically quarter wave, so compute the wave length using a formula above and then divide by 4. For example 72.000 MHz frequency band generically, ignoring decimal 1/4 Wave = 1.0409 meter (1040.9 mm) 1/4 Wave = 40.982 inch 72.270 MHz frequency, specifically 1/4 Wave = 1.0370 meter (1037.0 mm) 1/4 Wave = 40.829 inch All of the rx I saw, 72MHz, 53/50MHz, 27MHz, all have about 39 inches(1meter) of wire coming out of the box. So either they are tuned inside with some magic circuit or what? Brian RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
[RCSE] 555 antenna length
I need to add a new antenna to my Hitec 555. Broke the old one ages ago so I need the recommended antenna length. TIA David Z RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
I have a new one and it measures 40.5 from the case.. - Original Message - From: David Zucker [EMAIL PROTECTED] To: soaring@airage.com Sent: Tuesday, January 25, 2005 7:35 PM Subject: [RCSE] 555 antenna length I need to add a new antenna to my Hitec 555. Broke the old one ages ago so I need the recommended antenna length. TIA David Z RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
[RCSE] 555 antenna length
Date: Tue, 25 Jan 2005 21:06:01 -0800 From: Mike Reed [EMAIL PROTECTED] To: soaring@airage.com Subject: Re: [RCSE] 555 antenna length Message-ID: [EMAIL PROTECTED] I have a new one and it measures 40.5 from the case.. - Original Message - From: David Zucker [EMAIL PROTECTED] To: soaring@airage.com Sent: Tuesday, January 25, 2005 7:35 PM Subject: [RCSE] 555 antenna length I need to add a new antenna to my Hitec 555. Broke the old one ages ago so I need the recommended antenna length. TIA David Z That sounds about right. The calculation for a 1/4 wave antenna is len (in feet) = 234/freq (in mhz). Based on that I ran the numbers and got 39... 234/72 = 3.25 feet or 39 inches I'm sure the matching network adjusts for the extra inductance in the antenna from it being a bit to long. One thing I have not included was the velocity factor of the wire antenna which may have little or no effect, but would quite possibly shorten the antenna even more. I'd feel safe at 40 something inches. Kurt RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] 555 antenna length
- Original Message - From: David Zucker [EMAIL PROTECTED] To: soaring@airage.com Sent: Tuesday, January 25, 2005 9:35 PM Subject: [RCSE] 555 antenna length I need to add a new antenna to my Hitec 555. Broke the old one ages ago so I need the recommended antenna length. David, If you're fussy, the correct antenna length depends upon the frequency. Wavelength = Speed of Light / frequency In meters = 299, 792.458 / frequency in MHz In inches = 11,802,852.6771654 / frequency in MHz Quarter Wave = Wavelength / 4 R/C receiver antenna are typically quarter wave, so compute the wave length using a formula above and then divide by 4. For example 72.000 MHz frequency band generically, ignoring decimal 1/4 Wave = 1.0409 meter (1040.9 mm) 1/4 Wave = 40.982 inch 72.270 MHz frequency, specifically 1/4 Wave = 1.0370 meter (1037.0 mm) 1/4 Wave = 40.829 inch Higher the frequency, shorter the antenna. Note that the computed lengths are total, not just the portion sticking out of the receiver case. Total length will include any wire inside the case plus the length of trace on the PC board. Regards, Tim RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
