Very frustrated with my HT / rooftop antenna. Any hints?

Discussion in 'General Technical Questions and Answers' started by KM6KCM, Jun 26, 2017.

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  1. KM6KCM

    KM6KCM XML Subscriber QRZ Page

    Hello everyone,

    I'm dealing with a very frustrating HT / antenna issue, and I'm looking for advice on how to best troubleshoot it. Forgive me if I'm using incorrect technical jargon, since I'm still quite new at this.

    Upon receiving my technician license in late April, I began transmitting to various local repeaters using a 5w Baofeng HT (BF-F8+) with a 16" Nagoya NA-771 dual band whip antenna. I'm in Sacramento, at the bottom of a valley surrounded by repeaters.

    My first priority was to upgrade my antenna.

    I installed an Arrow Antenna VHF/UHF open stub J-pole antenna mounted about 10' above the highest point of my roof. The antenna runs through 100' of LMR-400 to my study. Here's a shot of the antenna setup (I've since secured the coax and grounded the antenna).

    My reception got a lot better at most of the repeaters I frequent, but it wasn't a 100% improvement -- I started hearing background FM music on one of my favorite repeaters, and reception got a lot worse on my other favorite repeater.

    I got advice that I should upgrade my HT, since the Baofeng's "cheap, untuned" front end (quoting a ham on reddit) was having intermod issues.

    I've since used both an Icom ID-51A Plus and a Kenwood Th-D72A at my home with my roof mounted antenna. The Icom reaches some repeaters better than the Baofeng or the Kenwood, and the Kenwood reaches other repeaters better than the Baofeng or the Icom. None of the three HTs I've used can reach all of the repeaters I want to use 100% of the time. These repeaters are all between 5 and 15 miles from my location.

    I'm getting especially frustrated because, all things considered, I'm getting the best, most consistent results with the Baofeng and whip antenna. The Icom (which I've returned) and the Kenwood (which I'm considering returning) simply aren't justifying their cost.

    Please assume for the sake of troubleshooting that I've programmed the radios correctly. Just in case this is a faulty assumption, here's a screencap from Chirp showing the settings I'm using on my Kenwood.

    Here's what I'm thinking of as potential sources of the issues I'm having, from most to least likely:
    1. Multipath interference?
    2. Intermod interference?
    3. The 100' run of LMR-400 is just too much for 5w HTs, even "good" ones like the Kenwood Th-D72A?
    4. Bad coax / Bad crimping job on the UHF connectors?
    These issues caused me to miss my local club's field day on Saturday, since I couldn't connect via the blasted repeater to get the non-public address from the club, which started a frenzy of frustrated troubleshooting. Weirdly (to me at least, maybe there's a simple explanation) is that my reception at this repeater is great -- I just can't transmit to the darn thing.

    I'm really at the point of pulling out my hair trying to deal with these issues. The antenna setup was $200 and several hours of labor, and the Kenwood HT I'm using was $390. This is a big chunk of money for me, and I feel like it was wasted money if I'm not seeing significantly better results than a $30 Baofeng with a $15 whip antenna.

    Thank you in advance for any advice y'all might have on these issues. Thank you for indulging my venting.

    73,

    Dan / KM6KCM
     
  2. KM6KCM

    KM6KCM XML Subscriber QRZ Page

    First "A-ha!" moment:

    I started thinking about how strange it was that I could clearly hear, but not transmit to, one of the repeaters I want to use. This suggested that I had the TX tone programmed incorrectly, but it looked correct in Chirp.

    I decided to double-check the radio's programming with the Kenwood MCP-4A utility on Windows, instead of Chirp on my Mac, and there's a discrepancy:

    The repeater is 145.19- MHz 162.2 PL.
    Chirp shows that these settings are correct.
    Querying the radio via MCP-4A utility, the tones are messed up. It's showing 145.19- MHz 167.9 PL, with a CTCSS frequency and a DCS code. Weird.

    First step is to check all of repeaters' programming in the MCP-4A utility and fix any incorrect entries. I'll be sending a bug report into Chirp.

    This obviously won't fix all of the issues I'm having, but it's a start.

    UPDATE: I checked all of the memory settings and radio settings in the MCP-4A utility. It seems like quite a few of the settings that displayed correctly in Chirp were offset by 1 in the MCP-4A utility. Examples: 167.9 was present on a lot of tones that showed as 162.2 in Chirp. The timezone offset was UTC-7 in Chirp, but read as UTC-6 in the MCP-4A utility.

    Phew. This explained a lot. It's not a 100% fix, but it's definitely progress.
     
    Last edited: Jun 26, 2017
  3. AI6KX

    AI6KX Ham Member QRZ Page

    My first thought was that 100 feet of LMR400 is not a great way to treat your 5 watts, but the loss is "only" 3 dB on 2 meters. Still, you better check your coax connections because the tone programming issues you mention don't seem to account for the reception problems you have.

    Can you try simplex contacts with locals to compare the roof antenna with the whip? That would remove the repeaters from the circuit and make your troubleshooting easier.

    Steve in Okinawa
     
  4. W5DXP

    W5DXP Ham Member QRZ Page

    Years ago, I had some of those same problems with my DJ-580 HT. Solved the problems with a DR-570 mobile Xcvr (45 watts on 2m).
     
    N3AB, K6CLS and KD8DEY like this.
  5. KM6KCM

    KM6KCM XML Subscriber QRZ Page

    Thanks for the reply! Simplex is great. Great audio reports, and I'm definitely getting better results (distance and quality) with the Kenwood using my roof antenna than I was with the Baofeng/whip.
     
  6. KM6KCM

    KM6KCM XML Subscriber QRZ Page

    Yeah, I've thought about this route a lot. I'm saving up for an Icom IC-7100, but it's going to be awhile.
     
  7. K6BRN

    K6BRN XML Subscriber QRZ Page

    Dan:

    Glad you are enjoying amateur radio. And the LMR400 coax you are using is very low loss - a much better choice at VHF/UHF than RG213 or RG58 for a 100 foot run. But here are a few thoughts about your evolving arrangement, should you wish to do some improvements in the future. First, using an HT as a base radio, even with an elevated, external antenna to help out, is a big compromise. HTs are prone to front end overload and consequent desensing and signal bleed through from nearby out of band signals, like the FM radio station that is giving you problems. A relatively large external antenna can make this much worse. Also, 5 watts, if the HT can even really produce that output consistently, is a bare minimum for hitting repeaters at 15 miles with full quieting, in many cases. A dedicated base/mobile unit with 25 watts or so out and good front end filtering will solve both problems. Next, a j-pole antenna is relatively low gain. Many like them, mainly due to their low cost. But higher gain vertical antennas are common and readily available that can easily provide 3-6 db more gain, compensating to a large degree for your cable losses, and then some. These two improvement, which require some investment, will make a major night/day improvement to your ability to hit repeaters and enjoy some good rag chews. Like all hobbies, amateur radio tends to draw enthusiasts into more and more improvements and investment in more and better equipment as they learn more and see what others can do with what they have. Its part of the fun, I think.
     
    N3AB likes this.
  8. KM3F

    KM3F Ham Member QRZ Page

    100 feet of coax and an HT is not good to begin with.
    Need more power to overcome that loss.
    Need an antenna with a higher radiation angle if all the repeaters are very high up in the area.
    You likely would do as well with a 5/8 wave vertical higher angle radiator on shorter coax closer to a radio that has at least 25 watts output even if the antenna is lower.
    Bottom line is to optimize all three parameters.
    Power level, coax length, antenna pattern.
    You may even eliminate the out of band interference.
    Trying to get away on the cheap shows these parameters up under certain conditions.
    Good luck.
     
    WA7DXZ and N3AB like this.
  9. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    1. The coax issue has been discussed. Do ANYTHING possible to shorten the run length by 10ft+
    2. Increase height by any amount over 5ft.

    3. Get a decent gain antenna instead of a wet noodle.

    My preference in verticals are the G-series from Hustler. About the highest gain you can get in a whip and built sturdy.
    G6-270 is dual band. The G6 and G7 singles series are great.

    A short 3 or 4 element yagi is light enough to be turned with an inexpensive TV rotor and is an excellent addition to a vertical. Great for simplex use. Remember to mount it vertically for FM mode.

    G6-270
    https://www.dxengineering.com/search/part-type/vhf-uhf-base-vertical-antennas/brand/hustler-antenna/product-line/hustler-base-model-g6-270r-vertical-antennas?autoview=SKU&N=4294952557+402137&sortby=Default&sortorder=Default
     
    Last edited: Jun 26, 2017
  10. WB4SPT

    WB4SPT Ham Member QRZ Page

    OK, so the "fixing" the coax run/loss will make the IMD worse. How close is the offensive FM broadcast station? How many watts? This is the first item of business. And yes, it may take a better radio or at least a HiPass filter.
    Sounds like these repeaters are essentially line of site, even "visible"?? Should be a piece of cake to hit them on Tx, but your Rx needs help. One out of the box idea is to get a pro radio and program it to the 2M band. Pull-out Motorola's are dirt cheap. Taxi, base, or HH in the 25kHz style anyway. If you go down this road, get all you need to program it. CPS, cable, ...

    I saw the pix, but can't figure why a 100' coax is needed on a 1 or 2 story ranch house?

    Cheap notch filter: RG58, whatever, coax cut quarter wave at 100MHz. Easy to try; if you know the exact FM broadcast freq. use that. don't forget velocity factor.
     
    Last edited: Jun 26, 2017

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