Home |
Search |
Today's Posts |
#21
|
|||
|
|||
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1 "Tam" == t-tammaru Tam writes: Tam Have you determined that the radio puts out the same power on SSB Tam (whistle) as when you tune up (on CW?) ? Jack No, but I'm not really concerned about SSB versus CW -- I'll Jack operate CW if that's what it takes, and it'll be incentive to Jack finally learn. Tam That's what I am concerened about. You may have a bad mic, or Tam just not modulating due to some failure. When I wasn't able to Tam get out, I could alwayds talk to locals. Try CW/carrier with your Tam friend. I've tried just keying up and I could be heard a mile away, but not twenty. Tam He doesn't have to know CW if you are on the phone and he Tam knows your frequency. I would do it on 10m, away from anybody Tam else. You know you can get 20 miles on CB with 5W, and you have Tam 100. Excellent point. Tam Tam/WB2TT Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAVj5KGPFSfAB/ezgRAqwUAKD1H78q6/xrXD5Nn3LS9noF+CQZ2QCg3GOI cWQRh6xwWdu1tY/dCsUvh4o= =03FT -----END PGP SIGNATURE----- |
#22
|
|||
|
|||
Keep us posted as to what you find out. We could try a sched if it works at
all. I have a lot of free long distance on my cell phone for coordination. I am in NJ. Tam/WB2TT There is no zero or dollar sign in comcast. |
#23
|
|||
|
|||
Jack Twilley wrote in message ...
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 "Tam" == t-tammaru Tam writes: Tam Jack, Have you determined that the radio is actually putting out Tam 100W? The light bulb test should give some indication. I have an MFJ Versa Tuner II which has a power meter. It's not laboratory certified, but the needle does go all the way up to 100 when I tune up and transmit. Well, you know the radio works... I can't get the wire any higher than it is right now at this current location. This is pretty much the best I can do, and this little antenna already totally fills my yard and the yards of each of my neighbors (with their permission). It's a multiband fan dipole with three pairs of legs, cut for 40, 20, and 10. Your antenna is *very* efficient on those three bands, unless you have coax or connection problems and power is not making it to the antenna. BTW, the 40 legs will work 15 ok, if you tweak the match with the tuner...Will be pretty efficient on 15 also as a 1.5 wl dipole. My current goal is to acquire a noise bridge and see where the antenna resonates, then trim the antenna as necessary until it resonates in the right places. Good idea. You shouldn't really need the tuner. After that, I'll look into feedline length modifications as necessary. Should be unneeded. If coax length radically varies SWR, you need a 1:1 balun or choke to cut radation from the shield. Hopefully those two approaches will resolve my current issue. Actually, I don't think you have a problem, assuming no coax or connector problems. Does the receive noise level, and signal levels sound fairly normal, or dead? I think the main problem is trying to work locally using ground wave, with an antenna that is poorly suited for that. But, you should usually be able to work 40m in the day, being it's mainly NVIS. 20 miles is a long way for a low horizontal dipole to work locally without the help of skywave. A purely horizontal antenna has no groundwave, if no vertical feedline radiation, etc. It has a space wave, but it's going to be hard to work 20 miles over the noise. If both of you had verticals, it would probably be easy. As far as comparing antennas, all you have to do is use a antenna switch, and see which is best on receive. Operation is reciprical 98.8 % of the time, so a transmit test is unneeded. You should be having no problems working 40m in the day, or even 20m to stateside stuff. 10m local will be very tough, but you should be able to work some skywave. A vertical is much better for 10m local. 20 ft high is high enough to work for medium distance skywave. Maybe not a barnburner, but it should be working for general gov work...I've run many lower than that when camping, and had no problems. If you can't hardly work *anyone*, I would check your connections, and coax , etc. Also, if you use the tuner for now, use the bare minimum inductance to get a usable match. That will help reduce tuner losses, which can climb to 20% or so if too much coil is used. I would eventually tune the antenna up, and dump the tuner. There is no real need for it, unless you go off far from where you normally have it tuned. IE: work some CW when the antenna is tuned for the fone band. MK |
#24
|
|||
|
|||
Jack Twilley wrote in message
BTW, if you have the legs in the same direction, and close together, coupling can be a problem. As one mentioned, always start with the lowest band first, and go up band by band. If you have a coupling problem, it will almost always be one of the higher band legs being effected by a lower band leg. You can usually get a usable match if you vary the wire length. Try to get each band under 2:1 SWR. I run multi leg dipoles here, but I run mine in different directions and have few coupling problems. IE: if I had a 40 dipole braodside E/W, I'd run the 20 dipole N/S. Sometimes if you do have a coupling problem, just moving the higher band leg a few feet can cure the problem. You will almost never see a higher band leg effect a lower band to any great degree. MK |
#25
|
|||
|
|||
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1 "Mark" == Mark Keith writes: [...] Jack I have an MFJ Versa Tuner II which has a power meter. It's not Jack laboratory certified, but the needle does go all the way up to Jack 100 when I tune up and transmit. Mark Well, you know the radio works... At least enough to move that needle, or to come in on my friend's DC-to-daylight receiver as I previously mentioned. Jack I can't get the wire any higher than it is right now at this Jack current location. This is pretty much the best I can do, and Jack this little antenna already totally fills my yard and the yards Jack of each of my neighbors (with their permission). It's a Jack multiband fan dipole with three pairs of legs, cut for 40, 20, Jack and 10. Mark Your antenna is *very* efficient on those three bands, unless Mark you have coax or connection problems and power is not making it Mark to the antenna. BTW, the 40 legs will work 15 ok, if you tweak Mark the match with the tuner...Will be pretty efficient on 15 also Mark as a 1.5 wl dipole. Providing the wires haven't stretched too much over the past six months, or something else that might be wrong. Oh, and yes, all of the dipole legs are coplanar, and I can't change that, so I'll have to be careful when I tune them. Jack My current goal is to acquire a noise bridge and see where the Jack antenna resonates, then trim the antenna as necessary until it Jack resonates in the right places. Mark Good idea. You shouldn't really need the tuner. I acquired an MFJ noise bridge with the help of Dave Platt, and here are the results from some rough measurements at the rig (not at the antenna!): Frequency Depth R X Expander Resistance Reactance Impedance 3.750 4 D +25 No 122 28.67 125.32 7.150 2 A/B -25 No 14 -20.17 24.55 14.175 0.5 A/B +175 No 14 30.85 33.88 21.225 4.5 E +150 Yes 903.88 663.97 1121.54 28.850 0.5 A/B -100 No 14 -38.54 41.00 "Depth" is a rough estimate of how deep the null was when the measurement was taken -- my rig has a 0-10 scale and the measurements began when the noise was around 7 or 8, usually. The next three columns were my readings, and the final three columns are the reported values, in ohms. The first thing to note is that the readings which resulted from the deepest nulls are the readings which provide the most reasonable impedances. This tells me that I'm getting sensible readings, although I do need more practice with the device -- it's terribly twitchy. I plan on trying to find the resonant frequency of the antenna over the next couple of days, with the goal of shortening (or lengthening) the individual wires this weekend. Jack After that, I'll look into feedline length modifications as Jack necessary. Mark Should be unneeded. If coax length radically varies SWR, you Mark need a 1:1 balun or choke to cut radation from the shield. I have two chokes in my feedline currently -- one about a foot from the antenna feedpoint consisting of eight or nine turns of coax about an air core (a Folger's coffee can was used for wrapping), and one about a foot from the rig consisting of three large type 43 ferrite toroids with three loops of coax passing through all three toroids. Jack Hopefully those two approaches will resolve my current issue. Mark Actually, I don't think you have a problem, assuming no coax or Mark connector problems. When conditions change for the worse with no obvious reason, I start to consider the possibility that a problem exists. I can't blame sunspots for everything, so I'm looking into how my antenna may have changed since it was installed. I just completed another test of my antenna. I set the antenna tuner to "bypass" so I could use its SWR meter without affecting the tuning. Then, for each of the five bands I want to use, I tuned up on the dummy load, then switched over to the real antenna and checked the SWR. Here's the results: Frequency Dummy Antenna 3.750 1:1 infinity 7.150 1:1 2.5:1 14.175 1.05:1 3:1 21.225 1.1:1 3:1 28.850 1:1 1.9:1 There may be a correlation between these SWR measurements and the impedance values shown above -- the three bands which had lower impedance values also have lower SWR values, but none of them look particularly healthy. Mark Does the receive noise level, and signal levels sound fairly Mark normal, or dead? My experience aside from working from this location is limited to Field Day, which isn't really helpful. On some bands I get tons of receive noise, on others I get less. Mark I think the main problem is trying to work locally using ground Mark wave, with an antenna that is poorly suited for that. But, you Mark should usually be able to work 40m in the day, being it's mainly Mark NVIS. NVIS is still a mystery to me, and I need to learn more about it. Mark 20 miles is a long way for a low horizontal dipole to work Mark locally without the help of skywave. A purely horizontal antenna Mark has no groundwave, if no vertical feedline radiation, etc. It Mark has a space wave, but it's going to be hard to work 20 miles Mark over the noise. If both of you had verticals, it would probably Mark be easy. As far as comparing antennas, all you have to do is use Mark a antenna switch, and see which is best on receive. Operation is Mark reciprical 98.8 % of the time, so a transmit test is unneeded. I don't have any antenna against which to compare this one, though. Mark You should be having no problems working 40m in the day, or even Mark 20m to stateside stuff. 10m local will be very tough, but you Mark should be able to work some skywave. I'm currently unemployed, so I've got time for this kind of testing. Tomorrow, I'll try 40, 20, and 10 in the morning (eight to ten), in the afternoon (two to three), at sunset (five to seven), and at night (nine to ten). I'll post the results tomorrow night. Mark A vertical is much better for 10m local. 20 ft high is high Mark enough to work for medium distance skywave. Maybe not a Mark barnburner, but it should be working for general gov work...I've Mark run many lower than that when camping, and had no problems. If Mark you can't hardly work *anyone*, I would check your connections, Mark and coax , etc. I've already talked about having checked connections. I really think the next step is to change the lengths, but I want to make sure I understand the noise bridge's results first. Mark Also, if you use the tuner for now, use the bare minimum Mark inductance to get a usable match. That will help reduce tuner Mark losses, which can climb to 20% or so if too much coil is used. I've always done that, but mostly because that's what the antenna tuner documentation says to do, not because I knew why. :-) Mark I would eventually tune the antenna up, and dump the Mark tuner. There is no real need for it, unless you go off far from Mark where you normally have it tuned. IE: work some CW when the Mark antenna is tuned for the fone band. MK That's exactly why I bought the tuner -- that, and so I'd have an SWR meter in the shack. Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAV/crGPFSfAB/ezgRAkUwAJ0b4Yci2sq7YZBvlmREkYJqH1tg5ACg8OcV iv6EbEpaiKJIaeTKMOqe9BI= =TIDD -----END PGP SIGNATURE----- |
#26
|
|||
|
|||
"Jack Twilley" wrote in message ... I tuned up on the dummy load, then switched over to the real antenna and checked the SWR. Here's the results: Frequency Dummy Antenna 3.750 1:1 infinity 7.150 1:1 2.5:1 14.175 1.05:1 3:1 21.225 1.1:1 3:1 28.850 1:1 1.9:1 Jack, I don'r have any experience with the noise bridge, but based on the SWR readings, I would do the following: Since you have no 80m radiator, ignore that band for now. Measure the SWR at 7.0 and 7.3+ to determine whether the 40m wire is too long or too short, and trim to size. Repeat at 14.0 and 14.3+, and 28.0 and 28.5(?), assuming you want the most used part of 10m. I guess you are useing the 40m radiator on 15. Tam/WB2TT |
#27
|
|||
|
|||
On Tue, 16 Mar 2004 22:58:46 -0800, Jack Twilley
wrote: I just completed another test of my antenna. I set the antenna tuner to "bypass" so I could use its SWR meter without affecting the tuning. Then, for each of the five bands I want to use, I tuned up on the dummy load, then switched over to the real antenna and checked the SWR. Here's the results: Frequency Dummy Antenna 3.750 1:1 infinity 7.150 1:1 2.5:1 14.175 1.05:1 3:1 21.225 1.1:1 3:1 28.850 1:1 1.9:1 Hi Jack, If you can, move the Dummy Load to the end of the transmission line and repeat the measurements. 73's Richard Clark, KB7QHC |
#28
|
|||
|
|||
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1 Richard, moving the dummy load to the end of the transmission line is an excellent idea, and I really wish I could do it easily, but the paint can I used doesn't have a handle. I'll try to work something like that out this weekend. Jack. (looks like I'll have *lots* of data) - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAWOOlGPFSfAB/ezgRArbSAJ46aSXQgtZOkjb2zU6Vs3wnEx8GhgCgsmzC v1WA2pHea6ULhVUlFDd715o= =2ocQ -----END PGP SIGNATURE----- |
#29
|
|||
|
|||
On Wed, 17 Mar 2004 15:47:44 -0800, Jack Twilley
wrote: Richard, moving the dummy load to the end of the transmission line is an excellent idea, and I really wish I could do it easily, but the paint can I used doesn't have a handle. I'll try to work something like that out this weekend. Jack. Hi Jack, This is where you could as easily use a 50 Ohm resistor and your noise generator. There would be less interfering signals to confuse the data. You could also throw a deliberate mismatch onto the end like a 200 Ohm resistor. What value is that? If you measured 1:1, it would indicate you have an extremely lossy line (which tends to smooth out mismatches and gives some antenna inventors that warm snuggly feeling that they have licked the experts). 73's Richard Clark, KB7QHC |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Inverted ground plane antenna: compared with normal GP and low dipole. | Antenna | |||
Mobile Ant L match ? | Antenna | |||
Poor quality low + High TV channels? How much dB in Preamp? | Antenna | |||
QST Article: An Easy to Build, Dual-Band Collinear Antenna | Antenna |