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5/8 WAVE BASIC QUESTION.
WHAT IS THE "COIL" USED TO MATCH A 5/8 WAVE VERTICLE? i MEAN WHAT IS IT
MADE FROM AND WHERE DO YOU GET THEM? |
Cecil Moore wrote: wrote: WHAT IS THE "COIL" USED TO MATCH A 5/8 WAVE VERTICLE? i MEAN WHAT IS IT MADE FROM AND WHERE DO YOU GET THEM? The end feedpoint impedance of a 5/8WL vertical is about 150 - j600 ohms. The coil is used as a loading coil to cancel that capacitive reactance and is usually tapped and fed at the 50 ohm point. Construction details for a 2m 5/8WL mobile antenna are contained in "The ARRL Antenna Book" which is an excellent first book on the subject of antennas. Here's what EZNEC sez about a 1/4WL Vs a 5/8WL vertical. 1/4WL 5/8WL -0.14 dBi at 26 deg. TOA 0.1 dBi at 26 deg. -0.75 dBi at 17 deg. 1.4 dBi at 17 deg. TOA Whether that 2 dB advantage at 17 deg. is worth all that extra effort depends upon what kind of operating you do. It can make a difference for CW DX. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- Is that the same as a 1/4 ground plane vs 5/8 ground plane? It is just I have seen 5/8 antennas advertised with gain. On another topic, Would it be bad to use RG6 for the antenna and radio? |
Cecil, W5DXP wrote:
"Construction details for a 2m 5/8 WL vertical mobile antenna are contained in "The ARRL Antenna Book" which is an excellent first book on the subject of antennas." I agree the "ARRL Antenna Book" is a must have! Mine is the 19th edition and I didn`t find the 2-meter band 5/8-wavelength vertical. But, I also have the 1987 edition of the "ARRL Handbook". The 5/8-wavelength vertical for 2 meters appears on page 33-28 of that book. Best regards, Richard Harrison, KB5WZI |
wrote:
Is that the same as a 1/4 ground plane vs 5/8 ground plane? Yep. It is just I have seen 5/8 antennas advertised with gain. They have a slight amount of gain IAOI they have a good ground plane. The additional gain of a well designed 5/8WL vertical is, IMO, only important for HF CW DX and QRP digital work. On another topic, Would it be bad to use RG6 for the antenna and radio? "Bad" is relative. RG6 is 75 ohms. When I was in high school, RG6 & RG11 were very popular. If a center-fed dipole has a feedpoint impedance of 73 ohms, then 75 ohm coax results in a very low SWR on the feedline. The mismatch, is this case, is at the source and is not anything to worry about. Of course, your SWR meter, calibrated for 50 ohms, will not display the correct SWR on the 75 ohm coax. In the '50's, if our transmitter's pi-net output would "load", our system was working just fine. Most of us didn't even own an SWR meter back then. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Depends on what band the antenna is for.
|
K9SQG wrote:
Depends on what band the antenna is for. Why? - 'Doc |
Cecil Moore wrote: wrote: Is that the same as a 1/4 ground plane vs 5/8 ground plane? Yep. It is just I have seen 5/8 antennas advertised with gain. They have a slight amount of gain IAOI they have a good ground plane. The additional gain of a well designed 5/8WL vertical is, IMO, only important for HF CW DX and QRP digital work. On another topic, Would it be bad to use RG6 for the antenna and radio? "Bad" is relative. RG6 is 75 ohms. When I was in high school, RG6 & RG11 were very popular. If a center-fed dipole has a feedpoint impedance of 73 ohms, then 75 ohm coax results in a very low SWR on the feedline. The mismatch, is this case, is at the source and is not anything to worry about. Of course, your SWR meter, calibrated for 50 ohms, will not display the correct SWR on the 75 ohm coax. In the '50's, if our transmitter's pi-net output would "load", our system was working just fine. Most of us didn't even own an SWR meter back then. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- If my swr meter wont work with 75 ohm cable, should I use rg58 thsn if I cant find rg8? |
wrote:
If my swr meter wont work with 75 ohm cable, should I use rg58 thsn if I cant find rg8? You could probably recalibrate your 50 ohm SWR meter to 75 ohms. Or if all you are using it for is to make your transmitter happy, leave it calibrated for 50 ohms. In the latter case, you are not measuring SWR. When a 50 ohm SWR meter indicates 1:1, it is looking into 50 ohms which is what the transmitter wants to see. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Cecil Moore wrote: wrote: If my swr meter wont work with 75 ohm cable, should I use rg58 thsn if I cant find rg8? You could probably recalibrate your 50 ohm SWR meter to 75 ohms. Or if all you are using it for is to make your transmitter happy, leave it calibrated for 50 ohms. In the latter case, you are not measuring SWR. When a 50 ohm SWR meter indicates 1:1, it is looking into 50 ohms which is what the transmitter wants to see. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- By the way, I bought a 2 meter/220/440 mhz swr/watt meter that reads radiated/reflective power. Is this a good meter to set swr? Are these hard to use? I found some rg8/u and it is kind of expensive but the concensous seems to be to use that if I want accuracy. |
wrote:
By the way, I bought a 2 meter/220/440 mhz swr/watt meter that reads radiated/reflective power. Is this a good meter to set swr? Are these hard to use? Easy to use, not so easy to understand. I found some rg8/u and it is kind of expensive but the concensous seems to be to use that if I want accuracy. Exactly what are your concerns? accuracy? losses? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Stryped wrote:
"---I bought a 2 meter/220/440 mhz, swr/wattmeter that reads radiated/reflected power." When you have forward power but no reflected power, you have a matched load. SWR with a matched load is 1:1. For other power ratios, there are charts, slide rules and a formula to convert a power ratio to an equivalent SWR. SWR is one measure of the reflection coefficient. If you have a directional wattmeter, you don`t need an SWR meter. Best regards, Richard Harrison, KB5WZI |
wrote in message oups.com... WHAT IS THE "COIL" USED TO MATCH A 5/8 WAVE VERTICLE? i MEAN WHAT IS IT MADE FROM AND WHERE DO YOU GET THEM? Lots of good answers. - so I'll add another 1.5 cents worth. The coil is at the bottom normally with enough windings (coils) to add the right amount of inductance that will help to make a 50-ohm source happy. MADE FROM COPPER - usually. YOU MAKEM' - if you want to have fun. Arrl website has an antenna handbook - and several volumes of 'The antenna Compendium" that can give you many hours of fun winding coils, building antennas, making up matching sections - and all that good stuff. One tool I found helpful in playing around with antennas and transmission line is an MFG 259 Antenna Analyzer. - and there are others out there, too. |
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