Norm I need you to do two more things: 1) Tell me where the measurements of the lengths of the coax were made to, were they to the edge of the molded tee block, or to the center of the block, and at the splice to the different coax cables, was the measurement to the center of the splice or at the edge of the shrink tubing? 2) I used Z measured data from a DB 224A (for the 150-162 range) in my inventory, of the physical dimensions of the dipole. Would you confirm the dipole dimensions of the antenna you are using, everything including the spacing to the mtg pipe, the overall length, the length from the center mounting bracket to each end of the dipole and the dimension of the center to center of the folded section. I want to confirm that I am using correct data in my calculations. Only one dipole dims. are necessary. A dwg would be nice. >From first go around the Smith Chart, it appears that to use or modify the >O.C. stub to optimize the impedance matching for use at 144-148 Mhz may >be unwise. I'm leaning towards adding a Tee adapter with stub at the feed >point connector, and if necessary modifying the length of the 106.5", 50 Ohm >feed line coax. If you somehow modify the O.C. stub and your results are >worse, then you have essentially destroyed the matching harness >usefulness. Please also advise the type of connector used at the feed-point, >"N" or "UHF". WA9ZZU
--- On Wed, 2/17/10, NORM KNAPP <nkn...@twowayradio.net> wrote: From: NORM KNAPP <nkn...@twowayradio.net> Subject: RE: [Repeater-Builder] DB224A new harness To: Repeater-Builder@yahoogroups.com Date: Wednesday, February 17, 2010, 10:35 PM The unknown coax type is/was VB-83 (35 ohm). The VB-8 is of course 50 ohm and the VB-11 is 75 ohm. I hope that is the info you needed. It would be great if you could figure out what the open stub is for and can we use that for adjustments. If you need more info, let me know. 73 Norm ____________ _________ _________ __ From: Repeater-Builder@ yahoogroups. com on behalf of allan crites Sent: Wed 2/17/2010 9:29 PM To: Repeater-Builder@ yahoogroups. com Subject: RE: [Repeater-Builder] DB224A new harness I tried to work backwards on a Smith Chart from the dipole to the 1/2 WL O.C. stub to determine a reason for the stub but it appears the unknown coax types are causing erroneous and confusing answers. Can you confirm the coax types shown on your diagram? a. --- On Wed, 2/17/10, NORM KNAPP <nkn...@twowayradio. net> wrote: From: NORM KNAPP <nkn...@twowayradio. net> Subject: RE: [Repeater-Builder] DB224A new harness To: Repeater-Builder@ yahoogroups. com Date: Wednesday, February 17, 2010, 3:57 PM I got the harnesses at no charge from Andrew. I contacted customer support and told them I had 3 fairly new DB224's (2 a models and a b model) that had water intrusion/contamina tion in the harness where they were supposedly seal by the factory. I offered pictures and they accepted. Upon seeing the photos they asked that I give them serial numbers and requested I send the defective harnesses to them. I did and they offered and I accepted replacement harnesses. The two db224's that I have (personally) are the A models. The B model belongs to my shop. I often end up with abandoned and or defective db224's and other antennas as I work for a two way land mobile dealer/shop. Unfortunately, I have yet to get any DB224e's or any DB304's, just tons of DB224a's and an occasional DB224b. Hats off to Andrew for shipping me free replacement harnesses. I am still gonna ScotchKote those moldings regaurdelss. If you look at the attached photoes from my initial post, you will see that the open 25" VB-8 (50 ohm) stub is 12.5" from the "T" where the top half and bottom halves of the harness come together, down the main feed to the hardline (or whatever you feed the antenna with). Last night I connected the Sitemaster up again and I noticed the the SWR will come down some when I firmly secure the harness to the mast with the metal tape. How far down remains to be seen. I will keep you posted. 73 and thanks! de N5NPO Norm
