Best Coax for 10 Meters?

Discussion in 'Ham Radio Discussions' started by KD9ANZ, Mar 30, 2016.

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  1. K4AGO

    K4AGO Ham Member QRZ Page

    75 ohm cable TV cable? I know it wouldn't matter with a tuner, but wouldn't 50 ohm cable be better? Please educate me.
     
  2. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

    For example let's examine a typical dipole antenna which by design actually presents a 72 ohm impedance at the feed point.

    So in this case, which coax cable is more suitable for connecting to this 72 ohm antenna?

    1. 50 ohm cable?

    2. 75 ohm cable?

    In terms of the history of coax feed line goes, it used to be determined that 30-36 ohm feed line was ideal for transferring maximum power to the antenna.

    Similarly it was determined that 75 ohms was ideal for reducing signal losses in the antenna system.

    So where's the balance between high power handling and low loss efficiency?

    Yup, you guessed it. 50 ohms..

    That explains why "radio transmitters" prefer using 50 ohm feed line and CATV systems prefer using low loss 75 ohm feed line.

    In terms of losses in your antenna system, in many cases it can be demonstrated that 75 ohm feed line can be just as good, if not superior than 50 ohm feed line.

    Case in point:

    Let's have a quick look at this attenuation chart and compare LMR-400 and RG-11 at 50 MHz.

    RG1-11vsLMR-400.jpg

    Not to mention that many 75 ohm feed lines are quad shielded and mass produced at a higher volume than 50 ohm feed lines which tends to lower cost.

    The only real benefit of using 50 ohm cable is because of higher power handling capability. However, if you're typically only running a few hundred watts it may actually be more beneficial to use 75 ohm feed line.
     
    Last edited: Apr 16, 2018
    WF7A and WZ7U like this.
  3. WA8UEG

    WA8UEG XML Subscriber QRZ Page

    I seriously doubt you have the knowledge, experience or Amateur Radio accomplishments.

    Your advice is helpful, although the difference of 10 or so watts on 10 meters to a dipole is not significant enough to make a difference with or without a band opening. If he is on the fringe area of a 10 meter repeater it might make a difference but since it's his first HF radio and 10 meter repeaters are pretty much dead in the water and he was looking for a inexpensive feed line RG58 will be just fine at 50'. RG8X is better, 9913, LMR 400, all better but certainly not necessary.

    Your derogatory comment is childish.
     
    KC8VWM likes this.
  4. K1FBI

    K1FBI Premium Subscriber QRZ Page

    So when do you expect the next major opening on 10 meters?
    Go back to collecting wallpaper; I'm not impressed.

    pat-on-back.png
     
  5. WA8UEG

    WA8UEG XML Subscriber QRZ Page



    Well since you asked let me school you on 10 meters.

    10 will start to improve some where around the end of 2019 and continue thru 2030 but it is open (like 6 meters) several time a week via sporadic E. What you need to do is listen to a beacon frequency (can you copy code?) if so listen for beacons on 28.200 - 28.300 if you can hear a beacon you can most likely make contacts, if you cannot copy CW monitor DX Maps and filter for 10 meters.

    I don't understand why you asked the question, should everyone ignore 10 meters because F2 openings are rare?

    As for yet another childish comment this time with a cartoon, in my post I was just stating fact your the one that made the personal & condensing comment about me.

    I operate weekly with a Harvey Wells TBS 50 & HQ-140 both of which I fully restored, a DX60/HG10 - MR-1 I fully restored and have restored several other receivers as well as operating my main station. I operate 6 & 2 meter SSB & CW, I have a article in this months Electric Radio and have written articles for other publications through the years, I have a commendation from the National Weather Service for outstanding service and am currently converting a Swan MKII to 6 meters as well as just replaced the driver and finals in a Atlas 210X and got it working like new for a friend who was told to put it on e-bay as for parts only so I do a little more than win contests, work DX and collect operating awards, although I do enjoy those aspects of the hobby as well. So please don't insult me by saying go back to collecting wall paper!!!

    Your cartoon is degrading and insulting, grow up.
     
  6. K1FBI

    K1FBI Premium Subscriber QRZ Page

    Your overinflated ego is worthy of the "cartoon" and your post only validates it further.

    aw_selfesteem.jpg
     
  7. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

    Knock it off...
     
    W6GRD, W2AI and N3AB like this.
  8. WA8UEG

    WA8UEG XML Subscriber QRZ Page

    Done.

    I admit I don't take personal attacks well.
     
  9. WZ7U

    WZ7U Subscriber QRZ Page

    Other than the free coax Charles mentioned previously, anything not kinked too tightly or super UV checked should be OK. For low power, what you have in mind should be fine; but free is a very good price. If you insist on buying some, get something that will accommodate a higher power level/higher frequency for down the road. You won't regret it.
     
    K4PIH, K1FBI and KC8VWM like this.
  10. W5TTW

    W5TTW Ham Member Platinum Subscriber QRZ Page

    Depends on the antenna. For a multi-band dipole, go with ladder line. Almost forgot...Happy Birthday!
     
    VK6APZ likes this.
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