Linked dipole

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by M6HGN, May 15, 2018.

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  1. M6HGN

    M6HGN Ham Member QRZ Page

    Hi all.
    I have just purchased an ft 817 and I am going to make a linked dipole antenna as I can't afford an ATU as yet.
    My question is I have to resonate the sections. Do I buy a SWR meter to do this as I have read not to trust the built in SWR. If that what I do, does anyone know of a cheap SWR meter I can buy.

    Thanks in advance for any help.
     
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    There are many inexpensive SWR meters available on the new or used market, but the internal SWR meter in the FT-817 will work just fine for tuning your dipole. You don't need a lot of precision or a big easy to view SWR meter to tune a dipole, you just need to see that the rig can adequately load into the antenna and the built in SWR meter will be fine for that use.

    But if you really want an external SWR meter then there are many choices. In the states, there are very inexpensive SWR meters intended for the CB market that work just fine for use across the HF ham bands and a quick look at eBay shows many low price new and used SWR meters. They're simple instruments that are easy and inexpensive to build, you don't need fancy peak hold circuits or digital displays so just about any meter that covers the frequency range of interest will work fine. I could post links, but you'd be better of searching in the UK rather than buying a meter stateside and paying for shipping but any shop that supplies ham gear or Amazon, eBay or any of the typical online electronics retailers should carry a range of SWR meters. For instance a quick Google search turned up this on Amazon (stateside) which would work just fine: https://www.amazon.com/METER-Radio-Antennas-Jumper-cable/dp/B002KRME3C
     
    WB5YUZ likes this.
  3. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    You can certainly use the internal SWR meter for antenna trimming, it's reliable enough for that.

    But if you can afford it, you should also buy a medium-grade SWR meter and a dummy load. While it is possible to operate an amateur station without those two items, they are very handy to have around for antenna building and troubleshooting! Probably ninety-five percent of experienced hams have both in their shack.
     
  4. N8TGQ

    N8TGQ Ham Member QRZ Page

    Welcome to the forums! Do you have any radio clubs nearby? Many clubs have meters and analyzers you can borrow. Plus you can tap into a great resource of experience and knowledge. They could make short work of your dipole and they could use your support. Have fun!
     
  5. KC8VWM

    KC8VWM Ham Member QRZ Page

    I have used the built-in SWR meter in the FT-817 for tuning up antennas before.

    An external SWR meter is always better because it can detect smaller incremental changes in SWR occurring, but the one built-in to the FT-817 is certainly more than adequate and is good enough.

    I also have a linked dipole I use with my FT-817. It's a little more time consuming to construct compared to a single band dipole, but it turns out to be one of my favorite portable antennas.

    There's an online linked dipole calculator you can use for designing one here:

    https://www.sotamaps.org/extras.php

    Takes less that 20 seconds to switch bands and the SWR is always perfect on every band. I think you will enjoy using this portable antenna.
     
    Last edited: May 15, 2018
    K6BTM and NH7RO like this.
  6. WQ2H

    WQ2H QRZ Lifetime Member #214 Platinum Subscriber Life Member QRZ Page

    I agree with most of the folks here - if your dipole is even close it should work fine.

    I know my FT-991 can handle loads from 17-150 ohms (~SWR 3:1) - which actually is pretty robust. It has a feature where if it senses higher SWR - it stops and shuts the tuner off. You can still Tx - but the "High SWR" light will bark at you.

    Not sure if the 817 has something similar but my guess is that it does.

    Good luck !
    73
    Jim, WQ2H
     
  7. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    I generally use an old armaco swr meter. Recently when I was trimming the 20M dipole, I was too lazy to hook up the swr meter and used the one built in my ft757gx. I was adjusting out where the antenna (or is it antennae) is feed into the tower swtichbox.
    I have used my brothers mfj antennalizer to initially get the antenna in the right ball park. the swr meter allowed my to adjust for flat match at the desired operating freq. the freq in the mfj was possibly off. That armaco swr meter was pretty cheap back in 1970, still works
    seem to remember Archer made the same thing with the meter in a different spot
     
  8. M6HGN

    M6HGN Ham Member QRZ Page

    Thank you for all your advice, links and time :) it's very much appreciated.

    I will be joining a club which I think will be a good move as I can see how things are done and will understand things better.

    I didn't know I could use a CB SWR. I thought it had to cover more frequencies than the CB band. Also does the power setting matter. The ones I have seen have 10w as the lowest setting and I will only have 5w on my radio.

    That calculator for the antenna will be good to use. Thank you.
     
  9. KC8VWM

    KC8VWM Ham Member QRZ Page

    You can use a CB radio SWR meter with no problem at all.

    The FT-817 transmits 5 watts so it's well under the limits of any 10 watt capable SWR meter.

    So yes, you would use the 10 watt setting for a 5 watt radio.

    Also if you're building a link dipole, here's an idea describing how to make your own extremely cheap antenna insulators.

    https://forums.qrz.com/index.php?threads/making-wire-antenna-insulators.586568/

    I am using these insulators on my own linked dipole mostly because they are very strong and yet lightweight. Lighter antennas are easier to pack and carry for portable radio use.
     
    Last edited: May 15, 2018
  10. G6YYN

    G6YYN Ham Member QRZ Page

     

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