Topics

newbee here...just made the order...antenna question on old G5RV

Don - KM4UDX
 

Finally, after a year or more of hand ringing and second guessing myself, I finally pulled the switch and ordered my uBITX! 

 

Believe it or not, it came down to the ICOM7300 or the uBITX.  I picked the uBITX because I love to solder and build, and when things are hard, they are much more satisfying when you finally get over the hill.  And what I learn with the uBITX will apply to any more complex and capable transceiver downstream. So I pulled the plug.  Should start the build in a few weeks. Also ordered the normal white plastic case from BG, and bnc to SO239 connectors, etc.

 

Questions to the wise ones: Can I hook up the uBITX my G5RV? I have a length of coax (which has a simple choke) that connects to the twinlead, which then goes to the dipole aerial WITHOUT an antenna tuner?

 

I borrowed 100W transceiver, and the G5RV worked just fine. But the 100W rig had an internal antenna turner, which I’m told the G5RV needs.  The uBITX does not have a antenna tuner…will it work well enough directly connected with the G5RV?

 

If I have to get an antenna tuner…(rats!), then I’m thinking of the ZM-2 or the like.

https://steadynet.com/emtech/zm2-kit-uhf-connectors

 

Guidance please!

 

Thank you o wise ones!

 

Don

KM4UDX

 

 

 

From: John P
Sent: Sunday, July 1, 2018 3:04 PM
To: BITX20@groups.io
Subject: Re: [BITX20] BITX QSO Afternoon/Evening, Sunday, July 1, 3PM & 7PMLocal Time, 7277 kHz in North America, 7177 kHz elsewhere.

 

I'm calling CQ on 7277. Hearing nuttin but noise!

--
John - WA2FZW

 

Jerry Gaffke
 

You wanted wise ones, but I'll jump in till one shows up.

The uBitx will want to see 50 ohms, ideally under a 2 to 1 SWR, though I suspect it will
survive most anything if you power the IRF510's from not much beyond 12v.

The G5RV antenna is not resonant, the impedance it presents will be all over the map.
You really need a tuner between it and the 50 ohm coax to the uBitx.

That ZM-2 might be sufficient, I don't really know.


The fact that you cannot adjust inductance is not a plus in my book, that could be getting 
inefficient as frequencies go up and capacitive coupling between windings gets out of hand.
It claims to be good to 15 Watts, though does not really say under what conditions that might be true.
Max power it can handle will vary considerably with operating frequency and antenna impedance.

I'm happy enough with my MFJ-949E tuner/swr/dummyload
Build quality varies on the MFJ stuff, you want to lift the lid when you get it and check the solder job.

If you want to build your own tuner, you need an SWR indicator such as Diz's Tandem Match SWR indicator:
    http://www.kitsandparts.com/bridge1.4.php
Generally the tuner itself can be a couple tuning caps from some old tube type broadcast receiver
and a hand wound inductor with an alligator clip to tap into it somewhere, check the various handbooks on that.

For the price of the 7300, you can have a half dozen uBitx's go up in flames
and try out several MFJ tuners plus some homemade ones. 
And learn an awful lot in the process.

Jerry, KE7ER


On Sun, Jul 1, 2018 at 12:32 pm, Don - KM4UDX wrote:

Finally, after a year or more of hand ringing and second guessing myself, I finally pulled the switch and ordered my uBITX! 

 

Believe it or not, it came down to the ICOM7300 or the uBITX.  I picked the uBITX because I love to solder and build, and when things are hard, they are much more satisfying when you finally get over the hill.  And what I learn with the uBITX will apply to any more complex and capable transceiver downstream. So I pulled the plug.  Should start the build in a few weeks. Also ordered the normal white plastic case from BG, and bnc to SO239 connectors, etc.

 

Questions to the wise ones: Can I hook up the uBITX my G5RV? I have a length of coax (which has a simple choke) that connects to the twinlead, which then goes to the dipole aerial WITHOUT an antenna tuner?

 

I borrowed 100W transceiver, and the G5RV worked just fine. But the 100W rig had an internal antenna turner, which I’m told the G5RV needs.  The uBITX does not have a antenna tuner…will it work well enough directly connected with the G5RV?

 

If I have to get an antenna tuner…(rats!), then I’m thinking of the ZM-2 or the like.

https://steadynet.com/emtech/zm2-kit-uhf-connectors

 

Guidance please!

 

Thank you o wise ones!

 

Don

KM4UDX

Ralph Mowery
 

With almost any antenna designed to work over a large frequency range you will need a tuner of some sort.  Either a built in one or external.
The G5RV is not really that good of an antenna for all bands.  It was designed for 20 meters and a certain pattern.  It will give a reasonable SWR over many of the ham bands, but still a tuner is needed.  I like an off center fed antenna for working most ham bands .  It still needs an antenna tuner.  Look for the plans of a Carolina Windom if you want to build one.

As you are going to need a SWR bridge I wold look at a tuner that has a SWR meter built in.  Much as I hate say it about getting a MFJ, that may be the best for the dollar.  Open it up and check for loose parts and bad solder connections.  Lots of the mfj stuff seems to be about 99% built. and you need the extra 1%.
LDG makes some good automatic tuners at a reasonable price.

73 de ku4pt





On Sun, Jul 1, 2018 at 3:32 PM, Don - KM4UDX <dontAy155@...> wrote:

Finally, after a year or more of hand ringing and second guessing myself, I finally pulled the switch and ordered my uBITX! 

 

Believe it or not, it came down to the ICOM7300 or the uBITX.  I picked the uBITX because I love to solder and build, and when things are hard, they are much more satisfying when you finally get over the hill.  And what I learn with the uBITX will apply to any more complex and capable transceiver downstream. So I pulled the plug.  Should start the build in a few weeks. Also ordered the normal white plastic case from BG, and bnc to SO239 connectors, etc.

 

Questions to the wise ones: Can I hook up the uBITX my G5RV? I have a length of coax (which has a simple choke) that connects to the twinlead, which then goes to the dipole aerial WITHOUT an antenna tuner?

 

I borrowed 100W transceiver, and the G5RV worked just fine. But the 100W rig had an internal antenna turner, which I’m told the G5RV needs.  The uBITX does not have a antenna tuner…will it work well enough directly connected with the G5RV?

 

If I have to get an antenna tuner…(rats!), then I’m thinking of the ZM-2 or the like.

https://steadynet.com/emtech/zm2-kit-uhf-connectors

 

Guidance please!

 

Thank you o wise ones!

 

Don

KM4UDX


Jerry Gaffke
 

I've heard good things about the G5RV.
Never had one.
Since you got one up, I suggest you go ahead and use it.
It is resonant on 20m, will give a 50 ohm match there if the ladder line is cut to the correct length.
I would recommend at least borrowing an SWR meter to determine
over what range of frequencies it gives a reasonable match.
For multiband use on the G5RV you do need a transmatch of some sort, but it could be cobbled together cheaply.
Ladder line has much less loss than coax even at high SWR, so a transmatch between the ladder line and the coax
can make this an efficient multiband antenna system.

Ralph's off-center fed dipole can be easier to put up than a center fed dipole, but does require a transmatch.
The end-fed is an extreme case, I have one of these:
    https://myantennas.com/wp/product/efhw-8010/
That particular EFHW is done well, is a good radiator, and with the matchbox provided can give
a good 50 ohm match across most of the HF ham bands with no tuner. 
I would still recommend having an SWR meter to determine if things are working properly.
If you might have ice loading in the winter then going to heavier antenna wire is a good idea,
buy the MEF-330-1k matchbox and the 14 gauge antenna wire separately:
    https://myantennas.com/wp/product-category/accessories/wire/
    https://myantennas.com/wp/product-category/antennas/efhw-transformers/
Check out the March 2016 QST review:
    http://www.arrl.org/files/file/ProductReviewsForDeb/2016/pr032016.pdf

Jerry


On Sun, Jul 1, 2018 at 01:55 pm, Ralph Mowery wrote:
With almost any antenna designed to work over a large frequency range you will need a tuner of some sort.  Either a built in one or external.
The G5RV is not really that good of an antenna for all bands.  It was designed for 20 meters and a certain pattern.  It will give a reasonable SWR over many of the ham bands, but still a tuner is needed.  I like an off center fed antenna for working most ham bands .  It still needs an antenna tuner.  Look for the plans of a Carolina Windom if you want to build one.