eHam
eHam Forums => MARS => Topic started by: WB4PBS on January 02, 2007, 09:43:53 PM
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The autotuner in my TS850 works great anywhere on 80 meters but will not tune outside the band even in manual. Has anyone had this problem? I may have to get an external tuner.
Randy
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It all depends upon what type of antenna you are attempting to match. It's quite possible the required match is outside the range of the internal tuner.
What antenna are you using? Are you trying to go above or below 80m?
Lon - NNN0OOR / NNN0GAW THREE
MDE Navy-Marine Corps MARS
Proudly Serving Those Who Serve
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The antenna is an 80 meter dipole that is resonant at 3650 and the tuner matches easily at 3998.
Randy
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<< The antenna is an 80 meter dipole that is resonant at 3650 and the tuner matches easily at 3998. >>
That's over 300kHz away! There aren't very many 80m dipoles that will have a 3:1 SWR bandwidth that wide. What is the actual SWR (as measured by an external SWR bridge) on 3998? I bet it's way higher than 3:1.
Trying to go about 4 mHz may well be outside the matching range of the internal tuner. Most internal tuners aren't designed to match much over 3:1.
Lon - NNN0OOR / NNN0GAW THREE
MDE Navy-Marine Corps MARS
Proudly Serving Those Who Serve
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Hi Randy,
It has a lot to due with just how much you are asking the poor ATU to deal with, most of the internal radio ATU's have a narrow range of 5-150 ohms resistive randge or a 3.1:1 VSWR that they can handle. Some newer latched relay design units found inside some make model radios as well as available as third party add on units have much wider tuning ranges.
Some Kenwood models are notorious for poor internal ATU's, actually most of the internal ATU's in ham rigs are rather poor in one way or another. The TS-930S had the first ATU in the ham radio world, what a stinker it was, I have one, glad it was in a used TS-930S and not the one had bought new back when!
Anyhow, the TS-450 and TS-2000 are both saddled with poor ATUs. I do not know if the TS-850 as the same tuner as the TS-450 or not, I own two TS-450's and I have modified both of them. Its major issues are between 4-7Mhz and below 3.5Mhz (not rated for use at 160m). Between 4-7Mhz the logic in the radio drops out the needed inductance tap for 80/75m and goes to the 7Mhz+ tap, thus that logic line needs to be broken, for manual control its just a matter of cutting a ribbon cable and adding a toggle switch, the details can be found in an article that I wrote at:
http://www.n2ckh.com/MARS_ALE_FORUM/SITREP_NOV2004.pdf
With the TS-450 below 3.5Mhz there is not enough inductance either, and not room to add more. What works best is if the antenna system being used is rather broad to begin with and you are only improving it from a 2.1:1 or there abouts, with one of my antenna designs ( 400 foot random wire off 9:1 BAL-450 two starge RF transformer) where the VSWR starts to raise above 2.1:1 below 3.5Mhz, the TS-450 ATU has no problem that antenna down to 2.8Mhz, but something about the logic in the ATU requires a procedure be followed where you first tune at 3.501Mhz, then you can just down to 3.3Mhz and then 3.1Mhz and then in 100Khz steps, it will tune to less than 1.5 easily and works great but only if it has values to work with that are good from having tuned previsouly not to far away in frequency, I just did all of this to with the radio and that antenna to refresh my memory as I wrote this. For info on the antenna mentioned, I have detail in a document which is currently being updated with a third antenna, but last years update is at:
http://www.n2ckh.com/MARS_ALE_FORUM/AAR2EY_NVIS_ANTENNA.pdf
My recommendation, get a better ATU, the LDG AT200PRO of for full computer control the AT200PC which is my choice, its the best for MARS-ALE operations.
Good luck.
Sincerely,
/s/ Steve Hajducek, N2CKH/AAR2EY/AAA9DHT
U.S. Army MARS Deputy High Technology Coordinator
MARS-ALE Software Development Team Leader
Manager Club Station AAR2CAB Camp Evans, N.J.
aar2ey@marsale.org
http://groups.yahoo.com/group/MARS-ALE/
Disclaimer: The opinions expressed herein are my own and do not necessarily reflect the opinions or policy of U.S. Army MARS management, or the Department of Army.
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Thank you very much for the replies. I retired to the Philippines a few years ago so am not using the TS850 here. Thanks everyone.