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Re: NF of devices used in LZ1AQ Preamp

 
Edited

The NE46134 / 2SC3357 is an excellent RF-Transistor. These meanwhile obsolete transistors are widely used in the RF Stages of Elecraft radios, as for example in the K3. A very similar but newer transistor which is cheap and still in active production is the BFU590Q (SOT89) oder BFU590G (SOT223). Give'm a try.
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One of the reasons, why the 2SC5551AF besides of its superb noise figure became a legend, is its robust silicon structure. Its maximum Voltage ratings (40 V Ucbo, 30 V Uceo) is closer to a xx2222 than to other newer RF-transistors and makes them very reliable in active antenna applications. The junctions of a bipolar transistor behave like a Zener-Diode, exceeding the max. rated Voltages can irreversibly damage the device.
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regards
Fred
Re: cardioid loop antenna from Cross Country Wireless

 

I use an Aziloop located 400ft away from house at the bottom of a field in the clear and it works really well 1-10MHz,
Sharp nulls in loop mode from VLF to HF, but in K9AY mode it is limited by the performance of the size of K9AY.
My one is only 20ft across (diameter) and 15ft high and has up to 30dB groundwave f/b 1-4MHz.
A friend tried one close to his house and other antennas and understandably it did not work well in either s/n or bearing accuracy, a remote Wellbrook was better.
John
Re: NF of devices used in LZ1AQ Preamp

 

Thanks Hisami, the 4703 certainly looks promising. It is available over here from LittleDiode, a UK supplier on Ebay, but rather expensive so I will give that one a miss.
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However, I have just found another "old stock" SOT89 transistor available for a reasonable cost (?6.95 for 10) from another UK Ebay Supplier (In-Stock-Components) 2SC3357 which has an even lower published NF so I shall add that to my "test" list.
Again only 12v max but has IC up to 100mA, diss up to 1.2W, and low published NF (1.1dB at 7mA and 1.8dB at 40mA with 10v Vce, at f=1GHz).
Its lowest frequency shown is 200MHz so I guess we will not find out how it performs at HF in the usual amplifier circuits (noting what Fred explained) until tested, but worth a try?
John
Re: NF of devices used in LZ1AQ Preamp

 

Hi John
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I have some genuine National Semiconductor 2222A's? I am happy to send you some if you are interested in wanting some reference units.
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Let me know, the postage is on me.
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Craig
Re: NF of devices used in LZ1AQ Preamp

 

Hi Mike ,
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Thanks for the advice.
I will take care.
The RSP Duo SDR I own has a 4.7V Bias-T.
It looks just fine.
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73, Hisami 7L4IOU
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Re: NF of devices used in LZ1AQ Preamp

 

Hi Martin,
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Thank you for pointing this out, I will check it.
According to the store's web, they have a significant inventory.
currently 790 bags, i.e. 3160 pieces.
I will buy some.
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73, Hisami 7L4IOU
Re: NF of devices used in LZ1AQ Preamp

 

On Mon, Oct 21, 2024 at 12:46 PM, hisami dejima wrote:
Could they be used for LF-HF loop amp?
Parameters look good. 2.5dB noise figure is good enough for HF.
The only issue is Vce max 12V. This means it is risky to use it in the most popular designs like LZ1AQ. The design should be modified to lower the supply voltage to 5V, the recommended voltage for this transistor. I consider this a plus, because the dissipated power is lower with the same collector current.
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73, Mike AF7KR
Re: NF of devices used in LZ1AQ Preamp

 

Hi Hisami,
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It may be worth trying some, but they seem to be listed as being obsolete, and don't appear to be widely available.
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Regards,
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Martin
Re: cardioid loop antenna from Cross Country Wireless

 

It's not much different from a Wellbrook and rotator in terms of cost, but it is much more sophisticated, and a lot of thought has gone into it's design.
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I think if you are interested in the LF bands, NDB or MW broadcast DXing, it's probably the best option, especially if you have limited space, or other restrictions.
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Regards,
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Martin
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On Sun, Oct 20, 2024 at 10:05 PM, Dave Martin wrote:

That's a lot of money for an antenna I have to build.?
Re: NF of devices used in LZ1AQ Preamp

 

Hi All,
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I was browsing for BJTs at Parts Shop in Akihabara.
There, a nice transistor called 2SC4703-NE46234? is available at a low price.
$0.66 for 4!
Could they be used for LF-HF loop amp?
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Hisami 7L4IOU
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Re: cardioid loop antenna from Cross Country Wireless

 

First derivative of frequency with respect to time is phase, so there are no analog wide bandwidth phase shifters, excepting for goniometers. Goniometers have an annoying amplitude variation with frequency, even in their capacitve form they are still tempermental. (Used to set the 3.579545 mhz carrier phase in RS-150 NTSC camera encoders and previously in WW2 radar sets.)
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US2496920A - Phase shifter
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If you are willing to create a matched pair of IF strips, with a +/- 45 degree difference at the IF freq, but with idetical phase matched RF front ends, it can work.
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But cost as the over all limit, digital is another matter and an SDRplay duo, which has the ability of 90 degree diversity reception might be the useful wide band answer.
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I would suspect that if you are willing to go "Non-Foster" then there is always an imaginary solution. . .
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The pun was intentional.? Get it? "i" or "j"? ?
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Jim/VEZ
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Re: cardioid loop antenna from Cross Country Wireless

 

I have the Cross Country Wireless v4, it has good nulls but you have to experiment with mounting orientation to get the best out of it.
Re: cardioid loop antenna from Cross Country Wireless

 

I saw their ad but didn't give it much thought.? That's a lot of money for an antenna I have to build.? Dave
Re: cardioid loop antenna from Cross Country Wireless

 

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Would you or anyone else know where a schematic diagram could be found for such a phasing network that could be used from ~15 kHz to 150 kHz?
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 10/20/2024 1:39 PM, Siegfried Jackstien wrote:

you maybe could add a telescopic whip and phase loop and whip together to have the null at the rear

dg9bfc sigi

Am 19.10.2024 um 15:09 schrieb Dave Martin:
I am.? I don't need gain in any one direction,? I'm looking for a deep notch to be used for direction finding.? On the current loop I'm using the null is deep but no front to back ratio is sometimes a problem.? Dave
Re: cardioid loop antenna from Cross Country Wireless

 

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you maybe could add a telescopic whip and phase loop and whip together to have the null at the rear

dg9bfc sigi

Am 19.10.2024 um 15:09 schrieb Dave Martin:

I am.? I don't need gain in any one direction,? I'm looking for a deep notch to be used for direction finding.? On the current loop I'm using the null is deep but no front to back ratio is sometimes a problem.? Dave
Re: cardioid loop antenna from Cross Country Wireless

 

If you want to go for the gold, have you thought of the Aziloop???https://quietradio.co.uk/

Nick
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On Sat, 19 Oct 2024 06:09:37 -0700, "Dave Martin" <kc7nj73@...> wrote:
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I am.? I don't need gain in any one direction,? I'm looking for a deep notch to be used for direction finding.? On the current loop I'm using the null is deep but no front to back ratio is sometimes a problem.? Dave
Re: cardioid loop antenna from Cross Country Wireless

 

I am.? I don't need gain in any one direction,? I'm looking for a deep notch to be used for direction finding.? On the current loop I'm using the null is deep but no front to back ratio is sometimes a problem.? Dave
Re: cardioid loop antenna from Cross Country Wireless

 

Its not remote steerable unless mounted on a rotator. Its an active loop antenna. Assuming you talking about the v4

Simon
cardioid loop antenna from Cross Country Wireless

 

Before I go out to modify, in the rain no less, my test antenna I wonder if anyone has experience with the somewhat directional loop from Cross Country Wireless.? Seems like an easy build.? It would be most useful to have a steerable notch instead of twisting knobs on a phasing unit.? Dave
Re: Tell my why I need a VNA?

 

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Thanks Mike

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Tom Anderson

SDR_Radio@...





On Oct 16, 2024, at 11:45?AM, Mike M <groups@...> wrote:

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I would say that if all you are designing are passive non-resonant antennas then a VNA may not be all that useful.
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However, if you are designing resonant antennas or any sort of filter then a VNA is essential. For resonant antennas the best way to tell where they are resonant is with a VNA. Filters, especially ones where you are winding toroids for inductors need to be tweaked to get best performance, and a VNA is the best tool for that.
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For active antennas it could be argued that a spectrum analyzer is better. It is if you want to do IMD measurements.
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As inexpensive as the NanoVNA and TinySA I would get both if you can afford them. Make sure you buy the "real" versions and not clones if you do. There are groups for both and resources to find a source for the "real' units.
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Mike M
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