Date   
Re: VK3YE AGC pcb.

Paul Galburt - K2AYZ
 

Nice feedforward audio limiter/compressor. Back in the day, when I designed professional audio gear, I sometimes used packages like this

https://www.ebay.com/itm/Xvive-Audio-VTL5C3-Opto-Coupler-/331920576160

for such applications. The main limitiations were transfer curve repeatability from unit to unit, limited overall dynamic range, and somewhat slow attack time for some applications.

Ultimately designs based on log characteristics of semiconductors worked better (like THAT 2180 part).

LED/LDR work fine here, except that sharp spikes will sneak throught the attack delay.

I have a batch of about 50 odd 2180's left from the old days that I hope to press into this service. These were kicked out of production THD tests on audio consoles where the limit was 0.005% THD.

73,

Paul K2AYZ

Re: End Fed antennas w/ uBITX #ubitx

Don - KM4UDX
 

Looks like the FA-VA4 is no longer sold? I was looking at that...

Re: VK3YE AGC pcb.

MVS Sarma
 

LDR and LED can better be tucmed into a small black tube. That helps intercerence from external lighting.


On Wed, 25 Jul 2018 6:35 PM Dexter N Muir, <dexy@...> wrote:

It may have been done before: an opto-coupler driven in a linear-transfer range ... ? Certainly smaller and less susceptible to ambient light (opening housing, etc. ... Just alter a few resistor values here and there ... may also be more readily available: scrap an old PC power supply.
73
Dex, ZL2DEX

Re: End Fed antennas w/ uBITX #ubitx

Mike aka KC2WVB <rb5363@...>
 

Warren,

I don't have the test equipment to precisely measure radiation of power off an antenna so I have to rely on others that do....

In a past life I would use a fan dipole fabricated for 80 meters, 40 meters and 20 meters and perhaps 10 meters as well. I no longer have the capability to use a fan dipole and will either have to use an end-fed random or half-wave antenna or really accept losses by using an interior small magnetic loop. 

I don't mind using the small magnetic loop for listening but I'd rather give an end-fed a go for transmission purposes. So, just to be clear are you suggesting that an end-fed half-wave antenna cut for 80 meters, roughly 64-66 feet, is most easily accomplished by using a tuner constructed as an L or T or Pi network? Are you also suggesting that were you to use an end-fed random wire antenna as opposed to end-fed half-wave wire antenna that the tuner approach as opposed to a transformer approach is most likely to give you the least in terms of loss?

On Tue, Jul 24, 2018, 11:07 PM Warren Allgyer <allgyer@...> wrote:
Allison

i agree with most of what you said. 

I have made extensive tests of the most commonly used 49:1 transformer as well as VNA analyses of both random and resonant end fed wires. I have not tested 9:1 transformers. 

90% and higher losses occur using the 49:1 transformer on non-resonant wires. If the wire is resonant the losses drop to on the order of 20%. In both cases the measured VSWR is severely and favorably distorted by the transformer losses.

What you you say about harmonically related bands is true in theory but not useful for the directly related HF bands because of the shortening effect of multiple half waves in series. This causes the second harmonic resonant point of, for example, an EFHW wire resonant at 7.1 MHz, to be well
above the 20 meter band. The wire therefore when used on 20 meters will be operating in the non-resonant mode with resulting 90% or more losses.

The EF wire itself, both in resonant and non-resonant configurations is an excellent radiator. The challenge is to deliver power to it effectively. This can be done very well if the wire is resonant with a transformer. It can also be done very well across a range of bands if a tuner is used rather than a transformer.

If  you put 100 watts into a non-resonant antenna fed by the popular  49:1 FT-250-43 toroid transformer, key down for one minute, the transformer will be too hot to hold. If you do it at 500 watts the core will explode. On the other hand, used with a resonant wire and on bands 40 meters and above, the transformer will be Weston but not alarmingly so. 

Re: VK3YE AGC pcb.

Dexter N Muir
 

It may have been done before: an opto-coupler driven in a linear-transfer range ... ? Certainly smaller and less susceptible to ambient light (opening housing, etc. ... Just alter a few resistor values here and there ... may also be more readily available: scrap an old PC power supply.
73
Dex, ZL2DEX

Re: End Fed antennas w/ uBITX #ubitx

 

Thanks for sharing your experiences with "end fed" antennas... I forgot to tell you my most favorite 20 / 10 meter antenna is a resonant loop of zip cord, strung up in the attic, fed with 300 ohm twin lead to a 4:1 balun.  It's very quiet and has low SWR on 20 & 10 meters. Works great except when it rains: then the water on the roof acts like a shield.
  I have noticed a huge difference in my many experiments with 9:1 vs. 49:1 ununs.  That would be noise.  The 9:1 is seems to be much more noisy... Have others noticed this?
  I spent many years building various antennas for the low bands and VHF.  The one gadget that I purchased (built from a kit) last year that made my life much easier was a "Vector Antenna Analyzer".  I bought the FA-VA4 which covers 100kHZ to 100mHZ.  It tells you in an instant what your antenna is doing at a specific frequency (or frequencies).  If you're getting serious about improving your antenna, consider buying or borrowing one.
  I'm still playing with end feds and plan to change my external end fed which (just like someone else who commented) is hidden underneath the wooden deck railing that runs the length of the house, yet this morning!
Your mileage may vary,
Jim W0CHL

Re: End Fed antennas w/ uBITX #ubitx

Gordon Gibby <ggibby@...>
 

Wow, that is incredibly useful information.   My concern about some of these designs has always been poor design with too short a piece of wire.   

20% loss is probably around one DB, no big deal. Probably similar to using a trap.   8 dB is completely different

Thanks!

Gordon KX4Z 




On Jul 24, 2018, at 23:07, Warren Allgyer <allgyer@...> wrote:

Allison

i agree with most of what you said. 

I have made extensive tests of the most commonly used 49:1 transformer as well as VNA analyses of both random and resonant end fed wires. I have not tested 9:1 transformers. 

90% and higher losses occur using the 49:1 transformer on non-resonant wires. If the wire is resonant the losses drop to on the order of 20%. In both cases the measured VSWR is severely and favorably distorted by the transformer losses.

What you you say about harmonically related bands is true in theory but not useful for the directly related HF bands because of the shortening effect of multiple half waves in series. This causes the second harmonic resonant point of, for example, an EFHW wire resonant at 7.1 MHz, to be well
above the 20 meter band. The wire therefore when used on 20 meters will be operating in the non-resonant mode with resulting 90% or more losses.

The EF wire itself, both in resonant and non-resonant configurations is an excellent radiator. The challenge is to deliver power to it effectively. This can be done very well if the wire is resonant with a transformer. It can also be done very well across a range of bands if a tuner is used rather than a transformer.

If  you put 100 watts into a non-resonant antenna fed by the popular  49:1 FT-250-43 toroid transformer, key down for one minute, the transformer will be too hot to hold. If you do it at 500 watts the core will explode. On the other hand, used with a resonant wire and on bands 40 meters and above, the transformer will be Weston but not alarmingly so. 

Does Howard's Power Output Mod Work on V4 uBitx?

RowlandA
 

I got very good results using Howard Fidel's 3 component power output mod on my V3 uBitx.  Due to other changes I made to the V3 board, I am not getting any power out at all (not related to Howard's mod), so I have a V4 board on order.

Howard, is your 3 component mod compatible with V4 boards, given that Farhan made a change to improve the 10M RF output level?

Thanks and 73,
Rowland K4XD

Re: End Fed antennas w/ uBITX #ubitx

Dave Dixon
 

right on the money thats what i useed for the past 5 years portable with a youkits hb1 now being replaced with a ubitx V3 Dave G0AYD

On 24 July 2018 at 22:23, Jim Reagan <jimreagans@...> wrote:
Not trying to start a "antenna war", but I noticed several people on this forum use "End Fed antennas".(Like Allison KB1GMX).  I have also used them with good success.  I feed them with 33' of coax and a 1:64 unun (PD7MAA design).  I have one with a trap (again PD7MAA blog) doing multiple bands.
On QRZ, everytime a End Fed topic is brought up, there is a bunch of nay sayers that always chime in. What are you experiences with them and QRP?  I'd like to know, being limited by an HOA, for antenna structures.
Thanks,
Jim W0CHL


Re: End Fed antennas w/ uBITX #ubitx

Warren Allgyer <allgyer@...>
 

At one hundred watts, key down for one minute, into a non resonant wire, the transformer becomes too hot to hold in your hand. On SSB however the duty cycle is so low the transformer does not overheat. The loss is there nevertheless. 

WA8TOD

Replacement audio amplifier?

m5fra2@...
 

If you want an easy fix for low audio output this might be the answer.

They claim 2W +2W, yes it is stereo. They are £1.06 post paid on ebay,
I got mine at a UK radio rally for £2. Not much bigger than a standard
volume control pot.

 

I have not tried it yet, should complete the wire up today and will see

what the audio level is like. If it is low I will change the AF gain pot for

the amp.

 

https://www.ebay.co.uk/p/Pam8403-Gf1002-Digital-Amplifier-Board-2-3w-Stereo-Module-USB-Power-470uf/848723847

 

Colin – M5FRA


Virus-free. www.avast.com

Re: End Fed antennas w/ uBITX #ubitx

m5fra2@...
 

EFHW antennas are so easy to make and very cheap!

 

Colin – M5FRA

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Thomas Owens
Sent: 25 July 2018 03:02
To: BITX20@groups.io
Subject: Re: [BITX20] End Fed antennas w/ uBITX #ubitx

 

A local ham was disposing of a SK estate and had a EFHW8010 for a great price. I purchased it and some other items from him, hung the EFHW8010 in the trees and was so pleased I ordered a EFHW4010 to take with me for travel, or field use. I figured I'd hang it in the attic for bad weather use. Testing it out with my 7300 (antenna is in my attic mind you), I got the following decode results on FT8 a few weeks ago. I think I'll keep it, thanks :)

Image removed by sender.


Virus-free. www.avast.com

Re: End Fed antennas w/ uBITX #ubitx

iz oos
 

In any case transformer loss by 2-3 db is huge if compared to the transmission line transformers by Jerry Sevick (which uses three ferrites and a 150ohm line for a 450:50ohm unun).


Il 25/lug/2018 09:48, ha scritto:

If then, the transformer would become very hot. Is that the case?


Il 25/lug/2018 09:44, "Warren Allgyer" <allgyer@...> ha scritto:
Jerry

i am aware of that product review and I have have discussed the methodology with the author. Their methodology was deeply flawed and cannot be duplicated in a properly equipped test laboratory. 

The antenna is not the issue. The transformer is. When feeding a resistive resonant load the losses in the transformer are under 2 dB for bands 40 - 17, rising above 3 dB or 50% on the rest of the HF bands. 

When feedingING a non-resonant reactive load the transformer loss rises to 10 dB and more on all bands. I am happy to supply test data and methodology, which has been independently corroborated, to any who wish to see it. I am good in QRZ. 

WA8TOD


Re: End Fed antennas w/ uBITX #ubitx

iz oos
 

If then, the transformer would become very hot. Is that the case?


Il 25/lug/2018 09:44, "Warren Allgyer" <allgyer@...> ha scritto:
Jerry

i am aware of that product review and I have have discussed the methodology with the author. Their methodology was deeply flawed and cannot be duplicated in a properly equipped test laboratory. 

The antenna is not the issue. The transformer is. When feeding a resistive resonant load the losses in the transformer are under 2 dB for bands 40 - 17, rising above 3 dB or 50% on the rest of the HF bands. 

When feedingING a non-resonant reactive load the transformer loss rises to 10 dB and more on all bands. I am happy to supply test data and methodology, which has been independently corroborated, to any who wish to see it. I am good in QRZ. 

WA8TOD


Re: End Fed antennas w/ uBITX #ubitx

Warren Allgyer <allgyer@...>
 

Jerry

i am aware of that product review and I have have discussed the methodology with the author. Their methodology was deeply flawed and cannot be duplicated in a properly equipped test laboratory. 

The antenna is not the issue. The transformer is. When feeding a resistive resonant load the losses in the transformer are under 2 dB for bands 40 - 17, rising above 3 dB or 50% on the rest of the HF bands. 

When feedingING a non-resonant reactive load the transformer loss rises to 10 dB and more on all bands. I am happy to supply test data and methodology, which has been independently corroborated, to any who wish to see it. I am good in QRZ. 

WA8TOD

Re: End Fed antennas w/ uBITX #ubitx

Jerry Gaffke
 

Warren,

You are correct, a poorly designed EFHW can have 90% losses.  Or worse.
But properly built, it can work well across multiple bands with very little loss.
Check out this QST review of the myantennas.com EFHW8010, it is resonant on 80,40,20,15, and 10m. 
    http://www.arrl.org/files/file/ProductReviewsForDeb/2016/pr032016.pdf

At the end of the review, they mention hooking two of these matchboxes back-to-back,
and finding there was virtually zero loss.

Here's a facebook page of experimenters playing with EFHW's:
    https://www.facebook.com/groups/EndFedHalfWaveAntennas/
Getting one to work well across multiple bands is not quite as trivial as one might think.
Just building a high powered transformer that works well from 3.5mhz to 30mhz is tough.

Jerry



On Tue, Jul 24, 2018 at 08:07 PM, Warren Allgyer wrote:
Allison

i agree with most of what you said. 

I have made extensive tests of the most commonly used 49:1 transformer as well as VNA analyses of both random and resonant end fed wires. I have not tested 9:1 transformers. 

90% and higher losses occur using the 49:1 transformer on non-resonant wires. If the wire is resonant the losses drop to on the order of 20%. In both cases the measured VSWR is severely and favorably distorted by the transformer losses.

What you you say about harmonically related bands is true in theory but not useful for the directly related HF bands because of the shortening effect of multiple half waves in series. This causes the second harmonic resonant point of, for example, an EFHW wire resonant at 7.1 MHz, to be well
above the 20 meter band. The wire therefore when used on 20 meters will be operating in the non-resonant mode with resulting 90% or more losses.

The EF wire itself, both in resonant and non-resonant configurations is an excellent radiator. The challenge is to deliver power to it effectively. This can be done very well if the wire is resonant with a transformer. It can also be done very well across a range of bands if a tuner is used rather than a transformer.

If  you put 100 watts into a non-resonant antenna fed by the popular  49:1 FT-250-43 toroid transformer, key down for one minute, the transformer will be too hot to hold. If you do it at 500 watts the core will explode. On the other hand, used with a resonant wire and on bands 40 meters and above, the transformer will be Weston but not alarmingly so. 

Re: Ubitx latest version board.. I need more audio to the speaker..

SV9CVJ Nikos
 

I use External PC Speakers for uBitx v3. Maybe i will try this amplifier later.  https://www.circuitsdiy.com/tda2003-amplifier-circuit-diagram/

Re: End Fed antennas w/ uBITX #ubitx

Kunjani Ol <loot@...>
 

I have tried many wire antennas, limited by the small space available.
About five years ago I tried an inverted L with a 9:1 unun and never looked back.
I use it for 160-17, then a modified CB vertical for 15-10.

I have the vertical section as far from the house as possible, which reduces noise appreciably.

The vertical section is supported be a 25 ft fibre glass pole, then it goes over the roof (touching the roof) and tied to a shrub in front of the house.

I have never used a counterpoise/radials, instead I purposely use the coax. I have 6 clip on ferrites which I move along the RG213 until I get the best SWR on all bands. It is easily tuned by the internal tuners on all rigs I have used on it (Yaesu and Icom)

I have recently made a 9:1 balun, and installed an earth rod at the feed point, and taken the ferrites off the coax (they no longer have any effect)
I can't detect any difference.

I don't think it can be bettered considering ease of building, simple supports, small size, ease of use and performance for price.

The transformer will get warm on high power on some bands, if you see the SWR drifting, you know things are getting warm.

Re: VK3YE AGC pcb.

Nick VK4PP
 

Maybe ill do an SMD version too...

Re: VK3YE AGC pcb.

MVS Sarma
 

Nice . I suppose we could try to make it smaller

regards
sarma
vu3zmv

Regards
MVS Sarma
 

On Wed, Jul 25, 2018 at 9:43 AM, Nick VK4PLN <nickpullen@...> wrote:
Something I'm Working on...




73 Nick VK4PLN