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Showing content with the highest reputation on 01/12/21 in all areas

  1. coryb27

    Duty Cycle Explained

    What does “duty cycle” mean? I bring up duty cycle every time I hear somebody talking about making a repeater out of cheap Chinese mobiles and worse any type of handhelds. Duty cycle is the maximum time an amplifier may transmit within a five minute interval, expressed as a percentage, to avoid overheating. Suppose a mobile amplifier is rated at 30% duty cycle. This means that it may transmit for no longer than 1.5 minutes and must remain off for not less than 3.5 minutes. Some people forget that a repeater is transmitting for 2 or more people, duty cycle will be reached quickly if you get into conversation. More people in the conversation just amplifies the issue. Once a radio reaches it's thermal design limits it will no longer be able to adequately cool the output transistors. Even if a radio is not hot to the touch the transistors are, in part because of the inefficient transfer of heat to the units housing or internal heat sink. The longer you exceed the duty cycle the more heat builds on the transistors, surrounding electronics and heat sink effecting it's ability to remain on frequency without spurious emissions. Exceed duty cycle long enough and you will need a new transmitter or radio. I have tested a few Baofang and TYT radios on my service monitor without great results. All of the radios started deviating outside of the allotted channel bandwidth after simulated conversation at 50% duty cycle, the longer I allowed this the worse if got. Testing was done using an Aeroflex 2975 IFR recently back from the calibration lab. GMRS is a tiny sliver of spectrum surrounded by the commercial land mobile part 90 service. It is important that any repeaters that are built or re-purposed are held to the highest standards and operated as to not cause any interference inside or outside of our allocated spectrum. I wont get into the part 90/95 debate but i do stand firm that non certified import equipment has no place on GMRS.
    1 point
  2. MacJack

    type accepted transceiver

    Since I'm newbie, I watch all the post... It looks like your Icom was replace with https://www.buytwowayradios.com/icom-ic-f4001-03-rc.html . Saying New version with Lithium-Ion Battery and Charger!. IMHO.. I got a two starter radios, KG-805G which is a CCP radio. Icom is Japanese. I am an old Motorola guy but they're not the same as they were years ago with all the gotcha. Did you see the posts on review of radios? https://forums.mygmrs.com/topic/2183-brand-name-radios-proscons-thread-usednew/?hl=icom https://forums.mygmrs.com/topic/2183-brand-name-radios-proscons-thread-usednew/page-2?hl=805g&do=findComment&comment=20996 Check it out... a lot of reviews so search the forum. I use more then 16 channels. I set my radio up to standard FRS and GMRS as well as the repeaters I can connect to plus a few GMRS channel low and high power with PL codes that we use as a family. Also a few travel repeaters... That added 6 more channel slots. So I scan all channels and go to any of the ones I want to connect with... The family is scanning as well and I tell them what channel to go to.... Works great. Happy investigating... Whatever you pick will be the best for you, so let us know what you did pick... My job done, to show you why 16 channel is a limit to how we use GMRS radio for our family needs. Jack
    1 point
  3. jsouth

    Midland MXT275 programming

    There are a few threads on this site with MXT 400 software and programming. Try this... https://forums.mygmrs.com/topic/1837-midland-gmrs-product-updates/?p=17118 I’ve used the software that’s available in that Dropbox and it works. Need a USB to 3.5 cable to program. This is the one I purchased... https://www.rtsystemsinc.com/USB-29A-Programming-Cable_p_748.html
    1 point
  4. mbrun

    Maximum GMRS Antenna Height

    I finally made the purchase of the HD 46’ push-up fiberglass mast I referenced in my earlier post. This weekend I rigged things up in a temporary way to conduct tests with local (and not so local) repeaters, as well as do some local simplex work. The image below shows my antenna at full elevation (56’ AGL to tip of Antenna). Mast was installed in a temporary way just for testing. Eventually it will get moved next to the house. Amazing how plumb the mast was being guyed only at 7’3” (not good long term, but good enough for testing). The antenna is a Comet 712EFC Collinear 9dBi. https://www.dxengineering.com/parts/cma-ca-712ef Cable is TMW LMR400 Mast is from DX Engineering. https://www.dxengineering.com/parts/dxe-tfk46-hd All of my testing consisted of using two handheld 5w radios. One feeding the Comet antenna, one in the car using an MXTA-26 antenna. First, the high-point of the testing. I was able to communicate from my home southeast of Cincinnati to the Dayton 700 repeater located 50 miles north(straight line distance) using approx 3 watts of input power into the antenna. Signal report from a Dayton area resident was “very good” and “into the repeater solid”, perfectly suitable for a QSO. That alone made my weekend. On the local front I was able to get into three local repeaters located 20, 21 and 26 miles way. Got in with full quieting to the one 20 miles away (“just as though I was next door”), and with just a hint of noise on the ones 21 and 26 miles away. Getting the antenna up high obviously makes a huge difference. On the simplex front I found I could achieve pretty reliable coverage out 4 to 5 miles where things transitioned to hit and mis out to about 7-8 miles when all seemed to die completely. I expect the reliable range will decrease as foliage comes back. Not bad though for a couple of lower power HT and with good external antennas. It will be nice to experience the positive change to simplex coverage after I up the power of the base and mobile to legal limits. Michael WRHS965 KE8PLM
    1 point
  5. jsouth

    Help - New Baofeng GMRS-V1 user

    Hello and welcome. I personally like to keep a few bubble pack radios on my bench for quick testing. That way I know that a new radio I purchased at least transmits and receives. Best of luck to you.
    1 point
  6. berkinet

    Finding PL code

    Sorry. But that is simply incorrect on 2 grounds. 1. Many ham repeaters are effectively private and do not publish their access requirements; and 2. Repeaters are not and have never been part of what you get rights to use with a GMRS license.
    1 point
  7. if you don't have it, the manual is here: https://midlandusa.com/wp-content/uploads/2017/10/MXT275-Owners-Manual.pdf out of the box, you probably have to enable the repeater channels in the menu (look for option 'rp' and set it to 'on'). next, pick the repeater you want to access, note the frequency and tone, and figure out which channel it equates to. (pg 27 has a chart of channel to frequencies). switch to that channel, then back into the menu, and you have to set the tones. page 28 has the code charts; see what code the tone equates to, and set it in the menu. from there, you should be set on the basics.
    1 point
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