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#1
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Greetings:
Building a 4 square antenna system: How should I tune each element? should I place a 50 ohm load on three elements then tune up one using my MFJ 259 after that element is tuned place the 50 ohm load on it then tune up the next element repeat till all have been tuned? OR should I short the other three elements to the counterpoise tune the element them repeat till all have been tuned? Or should the three be left floating then tune the one then repeat till all have been tuned? |
#2
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Peter Taggart wrote:
Greetings: Building a 4 square antenna system: How should I tune each element? should I place a 50 ohm load on three elements then tune up one using my MFJ 259 after that element is tuned place the 50 ohm load on it then tune up the next element repeat till all have been tuned? OR should I short the other three elements to the counterpoise tune the element them repeat till all have been tuned? Or should the three be left floating then tune the one then repeat till all have been tuned? It sounds like you're wanting to adjust their impedances. Why? You realize, of course, that as soon as they're all excited, the element impedances will change dramatically. One element in a typical 4 square array will actually have a negative radiation resistance. There's a lot of information about feeding phased arrays including 4 square arrays in Chapter 8 of the ARRL Antenna Book. It was completely re-written for the latest (21st) edition. ON4UN's _Low-Band DXing_ contains some good information also. Roy Lewallen, W7EL |
#3
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On Nov 4, 3:16*am, Peter Taggart wrote:
Greetings: Building a 4 square *antenna system: * *How should I tune each element? should I *place a 50 ohm load on three *elements * *then tune up *one using my MFJ 259 *after that element is tuned place the 50 ohm load on it then tune up the next *element repeat till all have been tuned? OR should I short the other three *elements to the counterpoise * tune the element them repeat till all have been tuned? Or should * the three be left floating * *then tune the one then repeat till all have been tuned? If you are using one of the commercial hybrid phasing networks or one designed from the 4u1un book proceedure then the normal method is this: 1. erect ONLY one vertical with its intended ground system. 2. feed it with 50 ohm line and adjust length for resonance at the center frequency you want 3. replace 50 ohm line with 1/4 wave 75 ohm foam coax (must be foam or 1/4 wave won't reach corners of standard 1/4 wave spaced elements) 4. build other 3 elements identical to the first one. |
#4
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On Nov 5, 7:26*pm, Dave wrote:
On Nov 4, 3:16*am, Peter Taggart wrote: Greetings: Building a 4 square *antenna system: * *How should I tune each element? should I *place a 50 ohm load on three *elements * *then tune up *one using my MFJ 259 *after that element is tuned place the 50 ohm load on it then tune up the next *element repeat till all have been tuned? OR should I short the other three *elements to the counterpoise * tune the element them repeat till all have been tuned? Or should * the three be left floating * *then tune the one then repeat till all have been tuned? If you are using one of the commercial hybrid phasing networks or one designed from the 4u1un book proceedure then the normal method is this: 1. erect ONLY one vertical with its intended ground system. 2. feed it with 50 ohm line and adjust length for resonance at the center frequency you want 3. replace 50 ohm line with 1/4 wave 75 ohm foam coax (must be foam or 1/4 wave won't reach corners of standard 1/4 wave spaced elements) 4. build other 3 elements identical to the first one. Dave Please forgive my ignorance but for the sake of my education would you flesh out number three some more. We used a four square for the 2008 field day and I watched the construction process very carefully but I don't recall what kind of seventy five ohm coax we used. Does using foam coax bring the velocity factor closer to one so that the cable is thus longer. I don't remember having any problem with the cable lengths but I freely admit I was functioning as labor rather than design or supervision. So maybe that had all been worked up in advance so those of us assembling the antenna didn't have to cope with it. I might well be putting my lack of education on display by asking this but it is the only way I will learn. Could you not use the right multiple of quarter waves and thus get the length you need with any seventy five ohm cable? I realize we would have increased the transmission line losses but would it be enough to be significant on say forty meters. That's what our four square was built for. When we were testing it weeks ahead of time it appeared to perform very well. We got at least two S units better signal reports when compared with a single vertical. -- Tom Horne, W3TDH -- Tom Horne, W3TDH |
#5
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On Nov 9, 2:28*am, Tom Horne wrote:
On Nov 5, 7:26*pm, Dave wrote: On Nov 4, 3:16*am, Peter Taggart wrote: Greetings: Building a 4 square *antenna system: * *How should I tune each element? should I *place a 50 ohm load on three *elements * *then tune up *one using my MFJ 259 *after that element is tuned place the 50 ohm load on it then tune up the next *element repeat till all have been tuned? OR should I short the other three *elements to the counterpoise * tune the element them repeat till all have been tuned? Or should * the three be left floating * *then tune the one then repeat till all have been tuned? If you are using one of the commercial hybrid phasing networks or one designed from the 4u1un book proceedure then the normal method is this: 1. erect ONLY one vertical with its intended ground system. 2. feed it with 50 ohm line and adjust length for resonance at the center frequency you want 3. replace 50 ohm line with 1/4 wave 75 ohm foam coax (must be foam or 1/4 wave won't reach corners of standard 1/4 wave spaced elements) 4. build other 3 elements identical to the first one. Dave Please forgive my ignorance but for the sake of my education would you flesh out number three some more. *We used a four square for the 2008 field day and I watched the construction process very carefully but I don't recall what kind of seventy five ohm coax we used. *Does using foam coax bring the velocity factor closer to one so that the cable is thus longer. *I don't remember having any problem with the cable lengths but I freely admit I was functioning as labor rather than design or supervision. *So maybe that had all been worked up in advance so those of us assembling the antenna didn't have to cope with it. *I might well be putting my lack of education on display by asking this but it is the only way I will learn. *Could you not use the right multiple of quarter waves and thus get the length you need with any seventy five ohm cable? *I realize we would have increased the transmission line losses but would it be enough to be significant on say forty meters. *That's what our four square was built for. *When we were testing it weeks ahead of time it appeared to perform very well. We got at least two S units better signal reports when compared with a single vertical. -- Tom Horne, W3TDH -- Tom Horne, W3TDH- Hide quoted text - - Show quoted text - the cable i normally use is rg-11u with foam dielectric, that gets the velocity factor up to .78-.80 so the cable is longer to get the required 1/4 wave. since the distance from the center to the corner of a normal 1/4 wave spacing 4-square is .707 of a wavelength the normal hard poly with a .66 velocity factor won't reach. |
#6
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On Nov 9, 5:51*pm, Dave wrote:
On Nov 9, 2:28*am, Tom Horne wrote: On Nov 5, 7:26*pm, Dave wrote: On Nov 4, 3:16*am, Peter Taggart wrote: Greetings: Building a 4 square *antenna system: * *How should I tune each element? should I *place a 50 ohm load on three *elements * *then tune up *one using my MFJ 259 *after that element is tuned place the 50 ohm load on it then tune up the next *element repeat till all have been tuned? OR should I short the other three *elements to the counterpoise * tune the element them repeat till all have been tuned? Or should * the three be left floating * *then tune the one then repeat till all have been tuned? If you are using one of the commercial hybrid phasing networks or one designed from the 4u1un book proceedure then the normal method is this: 1. erect ONLY one vertical with its intended ground system. 2. feed it with 50 ohm line and adjust length for resonance at the center frequency you want 3. replace 50 ohm line with 1/4 wave 75 ohm foam coax (must be foam or 1/4 wave won't reach corners of standard 1/4 wave spaced elements) 4. build other 3 elements identical to the first one. Dave Please forgive my ignorance but for the sake of my education would you flesh out number three some more. *We used a four square for the 2008 field day and I watched the construction process very carefully but I don't recall what kind of seventy five ohm coax we used. *Does using foam coax bring the velocity factor closer to one so that the cable is thus longer. *I don't remember having any problem with the cable lengths but I freely admit I was functioning as labor rather than design or supervision. *So maybe that had all been worked up in advance so those of us assembling the antenna didn't have to cope with it. *I might well be putting my lack of education on display by asking this but it is the only way I will learn. *Could you not use the right multiple of quarter waves and thus get the length you need with any seventy five ohm cable? *I realize we would have increased the transmission line losses but would it be enough to be significant on say forty meters. *That's what our four square was built for. *When we were testing it weeks ahead of time it appeared to perform very well. We got at least two S units better signal reports when compared with a single vertical. -- Tom Horne, W3TDH -- Tom Horne, W3TDH- Hide quoted text - - Show quoted text - the cable i normally use is rg-11u with foam dielectric, that gets the velocity factor up to .78-.80 so the cable is longer to get the required 1/4 wave. *since the distance from the center to the corner of a normal 1/4 wave spacing 4-square is .707 of a wavelength the normal hard poly with a .66 velocity factor won't reach. Dave So my guess was close but what about the rest of the question. Would any odd multiple of a quarter wave work as well except for the transmission losses it would introduce? Would three quarter waves work? -- Tom Horne. W3TDH |
#7
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On Nov 10, 5:57*pm, Tom Horne wrote:
On Nov 9, 5:51*pm, Dave wrote: On Nov 9, 2:28*am, Tom Horne wrote: On Nov 5, 7:26*pm, Dave wrote: On Nov 4, 3:16*am, Peter Taggart wrote: Greetings: Building a 4 square *antenna system: * *How should I tune each element? should I *place a 50 ohm load on three *elements * *then tune up *one using my MFJ 259 *after that element is tuned place the 50 ohm load on it then tune up the next *element repeat till all have been tuned? OR should I short the other three *elements to the counterpoise * tune the element them repeat till all have been tuned? Or should * the three be left floating * *then tune the one then repeat till all have been tuned? If you are using one of the commercial hybrid phasing networks or one designed from the 4u1un book proceedure then the normal method is this: 1. erect ONLY one vertical with its intended ground system. 2. feed it with 50 ohm line and adjust length for resonance at the center frequency you want 3. replace 50 ohm line with 1/4 wave 75 ohm foam coax (must be foam or 1/4 wave won't reach corners of standard 1/4 wave spaced elements) 4. build other 3 elements identical to the first one. Dave Please forgive my ignorance but for the sake of my education would you flesh out number three some more. *We used a four square for the 2008 field day and I watched the construction process very carefully but I don't recall what kind of seventy five ohm coax we used. *Does using foam coax bring the velocity factor closer to one so that the cable is thus longer. *I don't remember having any problem with the cable lengths but I freely admit I was functioning as labor rather than design or supervision. *So maybe that had all been worked up in advance so those of us assembling the antenna didn't have to cope with it. *I might well be putting my lack of education on display by asking this but it is the only way I will learn. *Could you not use the right multiple of quarter waves and thus get the length you need with any seventy five ohm cable? *I realize we would have increased the transmission line losses but would it be enough to be significant on say forty meters. *That's what our four square was built for. *When we were testing it weeks ahead of time it appeared to perform very well. We got at least two S units better signal reports when compared with a single vertical. -- Tom Horne, W3TDH -- Tom Horne, W3TDH- Hide quoted text - - Show quoted text - the cable i normally use is rg-11u with foam dielectric, that gets the velocity factor up to .78-.80 so the cable is longer to get the required 1/4 wave. *since the distance from the center to the corner of a normal 1/4 wave spacing 4-square is .707 of a wavelength the normal hard poly with a .66 velocity factor won't reach. Dave So my guess was close but what about the rest of the question. *Would any odd multiple of a quarter wave work as well except for the transmission losses it would introduce? Would three quarter waves work? -- Tom Horne. W3TDH- Hide quoted text - - Show quoted text - i 'think' so. since it adds an extra 1/2 wave delay to each of the elements and should result in the same impedance transformation it should work ok. it may be a bit more narrow banded since the impedance transformation would change faster with frequency, but probably not enough to notice. |
#8
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On Nov 10, 6:05*pm, Dave wrote:
On Nov 10, 5:57*pm, Tom Horne wrote: On Nov 9, 5:51*pm, Dave wrote: On Nov 9, 2:28*am, Tom Horne wrote: On Nov 5, 7:26*pm, Dave wrote: On Nov 4, 3:16*am, Peter Taggart wrote: Greetings: Building a 4 square *antenna system: * *How should I tune each element? should I *place a 50 ohm load on three *elements * *then tune up *one using my MFJ 259 *after that element is tuned place the 50 ohm load on it then tune up the next *element repeat till all have been tuned? OR should I short the other three *elements to the counterpoise * tune the element them repeat till all have been tuned? Or should * the three be left floating * *then tune the one then repeat till all have been tuned? If you are using one of the commercial hybrid phasing networks or one designed from the 4u1un book proceedure then the normal method is this: 1. erect ONLY one vertical with its intended ground system. 2. feed it with 50 ohm line and adjust length for resonance at the center frequency you want 3. replace 50 ohm line with 1/4 wave 75 ohm foam coax (must be foam or 1/4 wave won't reach corners of standard 1/4 wave spaced elements) 4. build other 3 elements identical to the first one. Dave Please forgive my ignorance but for the sake of my education would you flesh out number three some more. *We used a four square for the 2008 field day and I watched the construction process very carefully but I don't recall what kind of seventy five ohm coax we used. *Does using foam coax bring the velocity factor closer to one so that the cable is thus longer. *I don't remember having any problem with the cable lengths but I freely admit I was functioning as labor rather than design or supervision. *So maybe that had all been worked up in advance so those of us assembling the antenna didn't have to cope with it. *I might well be putting my lack of education on display by asking this but it is the only way I will learn. *Could you not use the right multiple of quarter waves and thus get the length you need with any seventy five ohm cable? *I realize we would have increased the transmission line losses but would it be enough to be significant on say forty meters. *That's what our four square was built for. *When we were testing it weeks ahead of time it appeared to perform very well. We got at least two S units better signal reports when compared with a single vertical. -- Tom Horne, W3TDH -- Tom Horne, W3TDH- Hide quoted text - - Show quoted text - the cable i normally use is rg-11u with foam dielectric, that gets the velocity factor up to .78-.80 so the cable is longer to get the required 1/4 wave. *since the distance from the center to the corner of a normal 1/4 wave spacing 4-square is .707 of a wavelength the normal hard poly with a .66 velocity factor won't reach. Dave So my guess was close but what about the rest of the question. *Would any odd multiple of a quarter wave work as well except for the transmission losses it would introduce? Would three quarter waves work? -- Tom Horne. W3TDH- Hide quoted text - - Show quoted text - i 'think' so. *since it adds an extra 1/2 wave delay to each of the elements and should result in the same impedance transformation it should work ok. *it may be a bit more narrow banded since the impedance transformation would change faster with frequency, but probably not enough to notice. Dave Thank you for your patience and courtesy with this technical neophyte. I hesitate to ask questions here because there is always at least one flame war in progress at any given time any I really don't want to cause or get caught up in one. -- Tom Horne, W3TDH |
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