There are other versions of 2n2222 in SMT, DXT2222.

The MMBTh10 is better than the 3904 as is the SMT 2n2369 (mmbt2369) and BFR106.

As to voltage that spot (Q90)should not see more than maybe 16V ever.

Allison

Mag loops...? Mis named.? ?Resonant small loop.

They run about -12db on 40M for a soso one and maybe -10db for a good one
compared to a dipole at 40ft or more.? This is for a 1M diameter loop at 40M? ?
The problem is radiation resistance is so low and other resistance in the
build can be significant.? Go up in frequency? Efficiency goes up but 80% is peak
as then you get to effects of uneven current distorting the pattern.

However the better the loop is the more tuning required as the bandwidth is narrow.
good for spurs and all and compact but like all small antennas (less than 1/10th
wavelength) they are inefficient.?

Its advantage self completing antenna, small,? has good null that can
help with noise reduction.

Oh we had a CME hit Saturday turning the bands upside down.

Allison

On Tue, Aug 28, 2018 at 08:48 AM, Ajay Kashikar wrote:

Can some one (who has used Myantenna or 49:1 home brewed EFHW antenna) share the experience if it was not working or any remidial action taken (added tuner) and which made it functional.

Ajay,
The map below shows most of my QSO's with a Myantennas EFHW-8010P fed with 50' RG8X direct from my ?BITX.

?
--

IF we don't take advantage of groups.Io for other topic centric groups we end up with mush.

Why do that?? Because people interested in antennas and not bitx interest will likely not look here.

Might as well start talking about old computers here rather than vintage computers forum.
After all the uBitx has a MPu and many of us worked with computers.

Allison

Ajay,

Just one clarification: You may use a 49:1 transformer or you may use a tuner. You do not need both.

Have fun!

WA8TOD

There is already a homebrew group and an antennas group. Splitting the radios up would just make a mess of things.

Vince - K8ZW.

--
Michigan VHF Corp.

开云体育

Cheers!

What we really need is an antennas group. Oh, wait...

Vince.

--
Michigan VHF Corp.

开云体育

Hi All,

What is the consensus for a SMT replacement for the 2n3904?

I note the MMBT10 only has Vceo of 25 vs 40 for the 2n3n04.

I really do not want to tack leaded parts onto the board.

My latest ubitx is only getting 2w out on 15m, and i want to improve
the 45 Mhz transistors, and the tx drivers.

Rod KM6SN

ps ofcom reduces qrm by limiting power to 400 watts for a full licence. intermediate are limited to 50 watts and foundation to 10 watts.. i thinkt that is the big linear amps which cause qrm

terry gm4dso

i agree that this approach is not ideal but without lab test equipment it is the best available and is within the requirements of the uk ofcom.
73 de terry gm4dso

I made the attached files for my own reference during work on my uBitx which I have now suspended. But I thought they might be helpful for those still engaged in trying to filter the radio with external LPF/BPF combinations. This was my uBitx with the filters completely removed so I could see what parameters would be needed for an external filter to work satisfactorily. There are four slides included. Here are my comments on each:

80,40,20 meter CW
- Power level set on each band individually to 5 watts
- Green display line represents the -43 dBc threshold
- Second harmonic on both 80 and 40 is somewhat problematic as are odd harmonics out to 13th

80,40,20 meter SSB
- Power level set on each band individually to 5 watts CW then 1 kHz tone input level adjusted to produce the same 5 watts
- Green display line represents the -43 dBc threshold
- Second harmonic on both 80 and 40 is somewhat problematic as are odd harmonics out to 9th

17, 15, 10 meter CW
- Power level set on each band individually to 2 watts
- Green display line represents the -43 dBc threshold
- Harmonics can all be removed with a simple 34 MHz LPF. The filter included in the uBitx is more than adequate

17, 15, 10 meter SSB
- Power level set on each band individually to 2 watts CW then 1 kHz tone input level adjusted to produce the same 2 watts
- Green display line represents the -43 dBc threshold
- 17 meter spurs represented by markers 1 and 2 are problematic because only a close spaced, single band BPF can be used to remove them.
- 15 meter spurs at the low end need to be addressed.
- A single filter cannot cover these bands because of the close spaced 17 meter spurs.
WA8TOD

Dear John I have already done a image conversionfor for the 3.5" Nextion with Microsoft Paint but I do not know how to change the x,y,h,w . If you have the same LCD I can send you the files.

Nikos Magafourakis

SV9CVJ

Yeah, 40 meters not so great for sure with qrp. I have worked dx on 40 with 100w. 20, 17, 15...gets progressively better. Agreed a proper size antenna is the way to go if possible

开云体育

Ajay,

This was addressed in this thread but I probably don't blame you if you don't want to read through several hundred posts and comments to find it.

The EFHW antenna with the 49:1 transformer works reasonably well on any band where the wire itself is resonant. That is not due to the resonance so much as to the very high impedance presented by a resonant half wave and the consequent good match to the 49:1 transformer. The reason the MyAntennas antenna MAY ( I have not tested it but I understand what they have done) is the wire is supplied with a six turn coil that effectively lengthens the antenna on higher, harmonically related bands. I suspect therefore it presents a resonant load on 80, 40, 20, and 10 meters. On bands where the wire/coil combination is not resonant, 60, 30, 17, and 12 meters, the system will show a deceptively low VSWR due to losses in the now mismatched transformer. The antenna will perform but as much as 90% of your output power will be converted to heat on these bands rather than radiating.

The homebrew antenna/wire does not use the carefully engineered coil and is therefore resonant on only one band, if even that. So this antenna, as recommended on the FB group, completely relies upon losses in the transformer to produce artificially low VSWR while converting the majority of your power into heat. If the wire is carefully cut to half wave resonance on any one band the system will show reasonable losses. It will not work well on harmonically related bands because of the shortening effect of multiple half waves in series which moves the frequency of resonant harmonics higher than the normal integer multiples.

In both cases, the MyAntenna wire and the homebrew wire, a simple LC tuner represents a better solution than the transformer. Typical losses using a tuner are normally well under 1 dB or less than 5%. Typical losses using a 49:1 transformer with a resonant wire are 1-2 dB (10 - 20%). Typical losses using a 49:1 transformer on bands where the wire is not resonant can easily be 10 dB or 90%.

In all cases a tuner represents the best performance.?

WA8TOD

It seems like an awful lot of added effort and complexity with little gain to me.

How about it? ? It is getting very hard to search and find posts just for the radio I have. ?