Date   

Re: New "ANTENNAS" group has been formed.

Arv Evans
 

Ken, and others...

and sign in.
Mail posts can be done from the group login or from email to:

This group needs at least a couple of moderators because I don't have time or
inclination to handle this and the BITX20 group at the same time. 
I would even transfer ownership to one of the moderators if someone wants to
take that on.

Arv
_._


On Fri, Aug 3, 2018 at 1:20 PM Ken <chase8043@...> wrote:
I'd like to be a member Arv.

Ken Chase
VA3ABN

Thanks

On Fri, Aug 3, 2018, 3:07 PM Arv Evans <arvid.evans@...> wrote:
A new group on groups has just been formed.

    https://groups.io/g/antennas/

It is for the purpose of general discussion of antennas and antenna designs. 
This is a relatively free-ranging group with limited moderation.  Please let me
know if you want to become a moderator.

Arv  K7HKL
_._


Re: New "ANTENNAS" group has been formed.

Ken
 

Sorry I thought it said member, not moderator.


On Fri, Aug 3, 2018, 3:07 PM Arv Evans <arvid.evans@...> wrote:
A new group on groups has just been formed.

    https://groups.io/g/antennas/

It is for the purpose of general discussion of antennas and antenna designs. 
This is a relatively free-ranging group with limited moderation.  Please let me
know if you want to become a moderator.

Arv  K7HKL
_._


Re: New "ANTENNAS" group has been formed.

Ken
 

I'd like to be a member Arv.

Ken Chase
VA3ABN

Thanks

On Fri, Aug 3, 2018, 3:07 PM Arv Evans <arvid.evans@...> wrote:
A new group on groups has just been formed.

    https://groups.io/g/antennas/

It is for the purpose of general discussion of antennas and antenna designs. 
This is a relatively free-ranging group with limited moderation.  Please let me
know if you want to become a moderator.

Arv  K7HKL
_._


Re: New "ANTENNAS" group has been formed.

Doug W
 

Thanks Arv.  I'm sure this new group will resonate with many of us.
--
www.bitxmap.com


Re: New "ANTENNAS" group has been formed.

ajparent1/KB1GMX <kb1gmx@...>
 

Thanks for starting that.

Allison


Re: any tips for debugging RFI issue? #ubitx-help

ajparent1/KB1GMX <kb1gmx@...>
 

Its 17.4 in free space for a perfect thin wire.   Multiply that by .95 for reality.
If you used 234/f  (234 .25W is half of 468 .5W) you get 16.62.  
Even antenna wires have velocity factor.

That's how.

Allison


New "ANTENNAS" group has been formed.

Arv Evans
 

A new group on groups has just been formed.

    https://groups.io/g/antennas/

It is for the purpose of general discussion of antennas and antenna designs. 
This is a relatively free-ranging group with limited moderation.  Please let me
know if you want to become a moderator.

Arv  K7HKL
_._


Re: any tips for debugging RFI issue? #ubitx-help

Mike KK7ER
 

Allison,

Thanks so much!  This is very, very helpful!  You have given me a lot of homework.  I will try the following and report back.
  1. Install air choke at matchbox (20ft RG8X wrapped tightly around a plastic jar).
  2. Attach counterpoise wire to ground lug of matchbox (I wonder why you specified 16.5ft.  My math gives 17.5ft for 1/4 wave at 14074 KHz.  I'll start with 17.5 and trim back).  I'll leave the counterpoise dangling to start and then find a way to hide it.
  3. Disassemble the uBITX and grind off the paint around the standoff and antenna holes and reassemble (no star washers in my junk box).
I'll leave the counterpoise-on-radio and antenna mods (shorten wire length to match table or use new matchbox  with longer wire) for phase two.

73 Mike KK7ER
 


Re: Interesting antennas for QRP

ajparent1/KB1GMX <kb1gmx@...>
 

I knew that.  Didn't know for sure it is was in use. Not everyone has that.

I have three cal sets, SMA, N, and BNC for that reason.  Also a set of precision mismatches.

Most PNA/VNA/ and my HP 4191AImpedance analyzer have a SOLT (short open load terminate)
procedure to cal out cables.  You cannot cal out current on the shield doing that.

I haven't used Kees VNA I have used the AIM 4170 and the miniVNA and both of those are
amazingly accurate.  The Rigol DSA815T does a good job as well if you have a good RLB or
Directional coupler.  Same cal procedure.

Allison


Re: BITX QSO Afternoon/Evening, Sunday, August 5, 3PM & 7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere.

Arvo W0VRA
 

On Fri, Aug 3, 2018 at 01:03 PM, Arvo W0VRA wrote:
CQ BITX W0RVO EM59, right?
No, because my callsign is W0VRA.  Sorry about that.


Re: BITX QSO Afternoon/Evening, Sunday, August 5, 3PM & 7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere.

Arvo W0VRA
 

If conditions are suboptimal, could we maybe CQ BITX by FT8 on Sunday evening?  I'm new to the mode, so I don't know if that's appropriate.   But I think the first TX would be (for me) CQ BITX W0RVO EM59, right?


Re: Additional Boards supplied with Case V3

Arvo W0VRA
 

On Thu, Aug 2, 2018 at 01:43 PM, <doncoulter@...> wrote:
...thee small pcbs that came with my kit...
Hello!

Can you post pictures of the small pcbs?  Did you mean "three pcbs" or "the pcbs"?

Thanks!


Re: Interesting antennas for QRP

Jerry Gaffke
 

Allison,

I haven't messed with it, but Kees' AQRP VIA includes the following feature:
"Calibration data (Open/Short/Load) is captured and recorded for all frequency steps between Start and Stop Frequency. This allows data to be recorded at the end of a transmission line, effectively eliminating the coax from the computed and displayed data. These data values are sent to the PC when requested."
That could avoid lots of trips up to the roof.  
Though I'd tend to do a direct measurement to confirm that measurements via coax are accurate enough. 
Jerry


On Fri, Aug 3, 2018 at 09:56 AM, ajparent1/KB1GMX wrote:
What I've done is make a bridge and actually measure the antenna wire and its pretty interesting
how it can vary with height.  That was an exhausting project due to need to drag gear to the yard
and build and validate a remote bridge.  Lots of up and down, batteries, and no small amount of
retesting to validate results.


Re: Interesting antennas for QRP

SV9CVJ Nikos
 

This is my portable antenna and coupler :  https://m0ukd.com/homebrew/baluns-and-ununs/end-fed-half-wave-antenna-tuned-coupler-efhw/

73 Nikos de SV9CVJ


Re: Tinny sounding electric miss on uBitx

ajparent1/KB1GMX <kb1gmx@...>
 

Its possible someone got standard HC49... not the shorter 49u like mine.  it actually does make a
difference as the quartz inside has a different cut.

Premium build, no.  It has all the bugs.

Allison


Re: Tinny sounding electric miss on uBitx

ajparent1/KB1GMX <kb1gmx@...>
 

Tim, your the go to then as you know know why its important. ;)

Yes the BITX (20/40/17...) are similar but not the same as uBitx.

The biggest change is the second conversion as that opens up
a few ways to alternately do things like change sideband.

Allison


Re: Interesting antennas for QRP

ajparent1/KB1GMX <kb1gmx@...>
 

That's worked for me at least.

Of the wire is already trimmed for say 14.2  changing the transformer should show a different SWR
for the real feed point resistance.  Resonance should not change for different transformers save
for internal wire lengths.   Of course we can tweak the wire to mask that but resonance suffers
and coax shield currents rise.

What I've done is make a bridge and actually measure the antenna wire and its pretty interesting
how it can vary with height.  That was an exhausting project due to need to drag gear to the yard
and build and validate a remote bridge.  Lots of up and down, batteries, and no small amount of
retesting to validate results.

Allison


Re: End Fed antennas w/ uBITX #ubitx

Doug W
 

On Fri, Aug 3, 2018 at 10:43 AM, Warren Allgyer wrote:
The fact that the antenna you have has resonances that fall at integer multiples says there is something else going on there. I suspect this is the function of the 6 turn inductor which would have the effect of electrically lengthening the wire, and lowering the resonant frequency, with greater effect at successively higher harmonics of the fundamental.
You pretty much got it.  That is how Danny (myantennas owner) explains it in a blog post at https://myantennas.com/wp/efhw-8010-is-this-the-ultimate-magic-antenna/ .  I referred to it way back in post 54967 but at the speed this thread was moving then it was easy to miss.
--
www.bitxmap.com


Re: any tips for debugging RFI issue? #ubitx-help

ajparent1/KB1GMX <kb1gmx@...>
 

That is a 1:9 random wire box.  Expect RF on the coax if the ground lug is not used with a .25 wave wire.

The SWR may be good with the wires in use but you have an off center fed antenna and RF on the coax
is not much better.    

For both grounding the braid and using a Air or ferrite choke at the ground point to the radio is advised.

Using a choke at the match box will require a counterpoise to be used or the antenna may be ineffective.
I also expect the SWR will change.  You need a .25 wave counterpoise with that matchbos and the coax
is not a good choice to do that service for the problems you are already having.

Your likely have a lot of RF on the coax and that is a source of the problem.
You are up against the wall (townhouse and all) for antennas and I get that.  

Things to try...

First and foremost use a counterpoise wire at the matchbox they provide a lug for that
the hanger hook is that in the picture.   The wire should be around 16.5ft for 20M.

Try attaching to the radio chassis itself a wire maybe 16-17ft (quarter wave) to force
the case to a current node (sorta ground).  Just lay the wire out straight on the floor
or ceiling (if ground floor) as a test.  See if that helps 20M (likely makes other bands worse)

One thing you might try is replace the matchbox with a vanilla 20M center fed dipole (two 16.5ft wires)
even if temporary.  If your high enough one of the wires can just dangle (forms a center fed inverted L).

Or replace the matchbox with a 1:49 type and use a 66-68ft wire (half wave end fed and working on harmonics)
You may still have RF on the coax but a lower magnitude and maybe less troublesome.

Also make sure the board and the connector are electrically connected to the metal case, try putting
the cover on as well but external wires will need to be choked with ferrite.

For 1:9 baluns there are a few magic lengths that work better for some bands or all.
table attached has that info.

Also that arrangement in the all band form requires a tuner at the radio as not all bands will match well.
A tuner does not help the RF in the shack issue, its there ot keep the final intact.

Let us know her if and of it helps.  I;m sure there are others having similar issues.

Allison


Re: Interesting antennas for QRP

 

Allison,

I can't speak for others, but the reason I use squares of integers is because I can do the math in my head:-) You are right, no reason why it can't be a different ratio, just means trimming the antenna length a little. Still, it would be best to keep the length of wire close to a theoretical 1/2 wave length for best efficiency, I would guess.Anything in the 1:36-64 range should be good for the transformer.

Joel
N6ALT