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2 Meter Band-Pass Filters for Front-End Overload

Discussion in 'Amateur Radio News' started by NJ7V, May 23, 2021.

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  1. NJ7V

    NJ7V Premium Subscriber QRZ Page

    Yes it it. Being from the area, you probably know that the range is South Mountain, with several named high points on the range like Mount Suappoa, Goat Hill and Maricopa Peak.
     
  2. K7CB

    K7CB Premium Subscriber QRZ Page

    Actually I didn't...I lived here for two years in 97/98 then just recently moved back in November. I never considered there were separate peaks with different names within that range. Now I know. I pass by it three times a week driving the 202 from the 10 on the east side up to the 10 on the northwest side.
     
    NJ7V likes this.
  3. K7CB

    K7CB Premium Subscriber QRZ Page

    Ironic you should mention Doug as I know who he is as well...he's been wanting me to take him up Thompson Peak to check some repeaters we (my employer) has up there.
     
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  4. NJ7V

    NJ7V Premium Subscriber QRZ Page

    I've hiked that peak and it was a beast. You must have the means to drive up there with something. Doug comes to Wednesday lunch at a church by my house. That's where I've visited with him of late.
     
  5. K7JEM

    K7JEM Ham Member QRZ Page

    Yes, I've known Doug for a long time, have not seen him in years though. I own many of the Cactus radio sites over here in southeast AZ and New Mexico, was just up on Heliograph Peak yesterday, 10,028 AMSL.
     
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  6. BA7LFI

    BA7LFI Ham Member QRZ Page

    My HF transreceiver often meet this situation.I can listen some broadcast HF radio of other frequency in 20m and 15m,these terrible signals make me annoyed!
     
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  7. W7MDN

    W7MDN Ham Member QRZ Page

    Charlie: Nice video. I learned something too.
     
  8. W1YW

    W1YW Ham Member QRZ Page

    That is correct. the radio is essentially a counterpoise part of the antenna, and this needs to be shielded in order to isolate the actual antenna from the radio.
     
  9. NC5P

    NC5P Ham Member QRZ Page

    I found that commercial (Part 90) single band radios seem to do better in high RF environments. You can get a decent Kenwood or Motorola analog HT pretty reasonable just to use for such situations.
     
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  10. K7NM

    K7NM Ham Member QRZ Page

    One approach since operation is "Portable" is to build a cavity resonator for the gain antenna feed. This can be done with solid printed circuit board, a piece of copper tubing and threaded stock with a couple of nuts. SO239s are put in one end for connecting coax in and out to the internal coupling loops which are adjusted in position and size for minimum insertion loss. The threaded stock on the other end adjusts a capacitor plate made of solid plated circuit board to adjust the resonant BPF frequency. Take it with you and your gain antenna and put it in line after tuned at home on the bench. The Q of this filter is very high. Q = F/BW (Frequency and Band Width). With an 8" on a side cavity (square) with a copper pipe center conductor (coaxial section) of 1/4 wave open on the tuned end, I have achieved Qs of nearly 900. Used similar ones made from Aluminum irrigation pipe on an FM commercial site in Montana with super performance. They are BIG relative to the ones in the video and would lay on the ground below the gain antenna. Just a suggestion. 73, Lee - K7NM
     
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  11. M7BLC

    M7BLC Ham Member QRZ Page

    So invest time and money in filtering on a less than $20 Baofeng ? Somehow my motivational curve sticks on zero :) .
     
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  12. W1YW

    W1YW Ham Member QRZ Page

    I disagree.

    Its a learning experience to solve a real world problem. Granted, some other HT's would not have the problem to this degree.

    The notion of 'overload' and even intermod are fairly foreign to most hams. Always a good idea to have fun understanding second order effects:)

    73
    Chip W1YW
     
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  13. W1YW

    W1YW Ham Member QRZ Page

    This is an extremely useful post. Keep it handy.

    73
    Chip W1YW
     
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  14. M7BLC

    M7BLC Ham Member QRZ Page

    For those with the expertise and inclination to experiment I would agree although I would just buy a better piece of equipment (as it is I will stick with my UV5R as for various reasons I do not go near big antennas) . Would not modification invalidate the certification on such units ?
     
  15. W1YW

    W1YW Ham Member QRZ Page

    Did you yourself say its just a ($20) Baofeng...?

    ;-)

    Heck yeh I modify my radios! Bet you do too:)
     
    Last edited: May 28, 2021

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