RT-100 OBSERVATION(S) AND QUESTION(S)
|
At the end of last year, I received an RT-100/RC-100 as a gift. I just finally installed it on my horizontal wire dipole about 170 feet in length. Feeding this wire with 30 feet of RG-8X. The tuner is connected to the shack via about 150 feet of LMR400DB.
?
During the auto-tuning process, I see the SWR value rising and falling as I would expect while the RT-100 is finding a solution. During this process I see the SWR hitting very low values, well under 1.5:1. What is confusing is when a solution is finally "locked in", typically it will land at anywhere from 2:1 to 5:1 instead of the lowest point scanned. Then when I re-key the radio, the tuning process begins again. Now, in many cases, I have the radio set at 100W. The fold back due to SWR drops the power to the neighborhood of 20-40W until a tuning solution is achieved.?
?
Using the ideal/proper tuning power of 10-30W, I can manually activate a re-tuning of the RT the tuner will find the lowest solution but when I resume the 100W setting, the tuner will often restart the tuning process. My solution for this is to turn off the power at the RC-100 so the tuner will remain at the solution. This somewhat removes the convenience of the auto-tuner idea for changing bands/frequencies.
?
The question, is this normal operation for this tuner or should I look for some issue? I have used the tuner on my vertical antenna (GAP) and my horizontal wire (dipole) with the same functional results. |
||
开云体育It appears that the real component of your line impedance is changing with power output … a little SWR change is understandable, but this cries for something either deteriorated on the line or its connects or a damaged coaxial cable, or a faulty connection. ? ? W4JDY / EM79xr / ITU 8 / CQ 5 ? ? From: [email protected] <[email protected]> On Behalf Of Dave Robinson via groups.io
Sent: Monday, February 17, 2025 5:21 PM To: [email protected] Subject: [ldgelectronics] RT-100 OBSERVATION(S) AND QUESTION(S) ? At the end of last year, I received an RT-100/RC-100 as a gift. I just finally installed it on my horizontal wire dipole about 170 feet in length. Feeding this wire with 30 feet of RG-8X. The tuner is connected to the shack via about 150 feet of LMR400DB. ? During the auto-tuning process, I see the SWR value rising and falling as I would expect while the RT-100 is finding a solution. During this process I see the SWR hitting very low values, well under 1.5:1. What is confusing is when a solution is finally "locked in", typically it will land at anywhere from 2:1 to 5:1 instead of the lowest point scanned. Then when I re-key the radio, the tuning process begins again. Now, in many cases, I have the radio set at 100W. The fold back due to SWR drops the power to the neighborhood of 20-40W until a tuning solution is achieved.? ? Using the ideal/proper tuning power of 10-30W, I can manually activate a re-tuning of the RT the tuner will find the lowest solution but when I resume the 100W setting, the tuner will often restart the tuning process. My solution for this is to turn off the power at the RC-100 so the tuner will remain at the solution. This somewhat removes the convenience of the auto-tuner idea for changing bands/frequencies. ? The question, is this normal operation for this tuner or should I look for some issue? I have used the tuner on my vertical antenna (GAP) and my horizontal wire (dipole) with the same functional results. |
||
|
All autotuners, especially remote, can do this, and for a variety of reasons, some of which have already been mentioned. 1. The tuner really wants to be at the antenna feed point, and instead of using a lossy run of RG-8X, which will see potentially extreme SWR losses and voltages, consider replacing that portion of the system with open-wire line. It works much better. 2. Depending on installation particulars, the outside of your coax can "receive" your transmitted RF, which can loop back through the system, continuously unbalancing the SWR detector in the tuner and calling for endless retuning cycles. If your system DOESN'T loop at 5W, that's a potential sign, as this condition is usually worsened with increasing power. 3. I consider it a 100% must to install a suitably sized ferrite-core RF choke at the tuner input (shack side of the tuner), and another similar choke at the radio, if necessary. I use 12-14 turns of coax (or parallel turns of 12-gauge house wiring, sometimes within Teflon sleeves) wound onto an FT-240-43 or FT-240-61 ferrite toroid, depending on whether I want 160-meter "choking." 4. Is it winter where you are? Little known fact: Most LDG autotuners DON'T WORK below about 10 F, and "tune looping" can occur. (MN owner of several LDG units, including the RT-100). I keep mine in a heated, insulated tote at the base of my backyard inverted-L. It's -15 F as I write this, and the temp inside my outdoor tuner box is still 20F, so it still works! Hope this helps, and best of luck, Kirk, NT0Z Rochester, MN My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)
On Monday, February 17, 2025 at 05:20:08 PM CST, Al Waschka <awaschka@...> wrote:
The SWR in the RG-8X is likely very high, creating a high current or voltage point with potential breakdown.? If you must run 30’ to the tuner I suggest 450 ohm open wire line. ? Al K5TAN ? From: [email protected] <[email protected]> On Behalf Of W4JDY1953_G via groups.io
Sent: Monday, February 17, 2025 5:48 PM To: [email protected] Subject: Re: [ldgelectronics] RT-100 OBSERVATION(S) AND QUESTION(S) ? It appears that the real component of your line impedance is changing with power output … a little SWR change is understandable, but this cries for something either deteriorated on the line or its connects or a damaged coaxial cable, or a faulty connection. ? ? W4JDY / EM79xr / ITU 8 / CQ 5 ? ? From: [email protected] <[email protected]> On Behalf Of Dave Robinson via groups.io ? At the end of last year, I received an RT-100/RC-100 as a gift. I just finally installed it on my horizontal wire dipole about 170 feet in length. Feeding this wire with 30 feet of RG-8X. The tuner is connected to the shack via about 150 feet of LMR400DB. ? During the auto-tuning process, I see the SWR value rising and falling as I would expect while the RT-100 is finding a solution. During this process I see the SWR hitting very low values, well under 1.5:1. What is confusing is when a solution is finally "locked in", typically it will land at anywhere from 2:1 to 5:1 instead of the lowest point scanned. Then when I re-key the radio, the tuning process begins again. Now, in many cases, I have the radio set at 100W. The fold back due to SWR drops the power to the neighborhood of 20-40W until a tuning solution is achieved.? ? Using the ideal/proper tuning power of 10-30W, I can manually activate a re-tuning of the RT the tuner will find the lowest solution but when I resume the 100W setting, the tuner will often restart the tuning process. My solution for this is to turn off the power at the RC-100 so the tuner will remain at the solution. This somewhat removes the convenience of the auto-tuner idea for changing bands/frequencies. ? The question, is this normal operation for this tuner or should I look for some issue? I have used the tuner on my vertical antenna (GAP) and my horizontal wire (dipole) with the same functional results. ?
|
||
开云体育For my long lead feeds for HF, I use a 1::1 isolator, problem solved. ? W4JDY / EM79xr / ITU 8 / CQ 5 ? From: [email protected] <[email protected]> On Behalf Of mike z via groups.io
Sent: Wednesday, 19 February, 2025 11:21 To: [email protected] Subject: Re: [ldgelectronics] RT-100 OBSERVATION(S) AND QUESTION(S) ? Couple of thoughts - Seems like a common mode problem. A choke ( here they are 10-11 turns of RG8x on an FT240-43 works on all my apps) at the antenna's feed point should help, as evidenced by an increase in the? problem happens at higher power. That would be my first choice. I've done this on G5RVs, ZS6s and an OCFD for 60-30-15M. A choke placed at the tuner's output may have an effect as well.? ? My ZS6 antennas have anywhere from 20 to 30 feet of RG8x from the feedpoints to the remote tuners, with the only choke at the window line to coax transition. The OCFD was miserable with out a choke placed at the building entry. ? The last concern is the length of your antenna. Perhaps a change would make a difference but, be aware that some would present impedances that would stress a tuner or be out of it's range. ? Mike N3PM ? |
||
|
Thank you, Mike. I placed a couple of toroids in the line, which seems to have made a difference.
I plan instead to use window line as I have several feet which I was planning for a future loop. Has anyone had experience with a balun for the transition to the tuner? Best choice would be what? 1:1, 4:1, or 9:1. Right up front it seems the choice might best be the 9:1 (450Ω:50Ω) but since the dipole is nonresonant, the impedance at the input to the feedline will be some other value. For reference, tThank you, Mike. I placed a couple of toroids in the line, and it seems to have made a difference.?
?
Instead, I plan to use window line since I have several feet available that I was originally saving for a future loop project. Has anyone had experience with a balun for transitioning to the tuner? What would be the best choice: 1:1, 4:1, or 9:1??
?
At first glance, the 9:1 balun (450Ω to 50Ω) seems like the best option, but since the dipole is nonresonant, the impedance at the feedline's input will likely be a different value. For reference, the wire length is about 170 feet, and the feedline will be 40 to 50 feet long.he wire is about 170' and the feedline will be 40-50'. |
||
Dave Robinson
W4JDY1953_G
Kirk Kleinschmidt, NT0Z