I would just like to understand what Tom is saying. I almost think he had
noise figure confused with noise temperature at one point.
Correction to my previous e-mail, first sentence in second paragraph.
should have said "When I studied preamps and NF ~30 years ago, I thought
the NF of the first
On a totally unrelated note, I cascaded two preamps to get 40 dB of gain
about 30 years ago. They were identical circuits, both using MGF-1202 GaAs
FETs.
The input was a Zener diode noise generator. The second preamp fed a 3dB
splitter which fed two inputs of a low-loss passive nulling circuit I
Pardon me for chiming in on this Waller flag discussion as I am probably the
least qualified person on Topband to discuss technical issues.
But, I do a lot of Trial and Error-ing and use some of the wisdom shared here.
Plus I am a true Ham O Holic and always want to improve my ability to work
Tom, I'm afraid I disagree but agree with some of that, I am using a
43dB
gain preamp since 2010 with not a single failure yet, but I understand
your
point. It is so delicate to implement that most of fellow that try it
fail.
Even aluminum enclosure does not shield it enough, 40 dB gain is
Above and beyond all the dialogue, JC is making these antennas work.
Time after time he is working stations that only a few with large
antenna systems copy.
73
Bruce-K1FZ
It seems unlikely most compact antennas are being used in locations so quiet
they need 30 dB gain, or .6 dB
There seems to be something that I'm missing in this preamp NF discussion.
When I studied preamps and NF ~30 years ago, I thought the NF of the system
of the first active device was the all-important thing. Whatever losses
were between the antenna feedpoint and the preamp input (coax, connectors,
There is no question in my mind that he is, Bruce.
I would just like to understand what Tom is saying. I almost think he had
noise figure confused with noise temperature at one point.
Correction to my previous e-mail, first sentence in second paragraph.
should have said "When I studied preamps
And if you look at US Patent 2,247,743, it
appears that Harold Beverage conceived of a horizontal Flag around 1941.
best wishes,
Nick
At 21:52 06-09-15, you wrote:
Bruce wrote on Sept 6. Snip < Check it out
http://www.qsl.net/k4fk/presentations/WF-receiver-antennas-SFDXAs.pdf
> Bruce, ref
I find them at hamfests, typically for a buck apiece. I've also seen
suggestions that they can be found at thrift shops.
73, Jim K9YC
On Mon,9/7/2015 5:08 AM, James Rodenkirch wrote:
Any suggestions, Jim, on where to find small, inexpensive linear
supplies to replace the wall warts?
> "I've replaced all of the SMPS blocks that came in my door with vintage
linear supplies (and some are vintage linear supplies float-charging
sealed lead acid batteries. 73, Jim K9YC"
Same here. For wall-mounted power supplies, Jameco has an excellent
selection of regulated and
Of Arthur
Delibert
Sent: Sunday, September 06, 2015 1:40 PM
To: topband@contesting.com
Subject: Topband: Waller Flag Question
The on-line materials about Waller Flags says that a modest size WF would
need about 40 dB of gain to boost the signal to a usable level. One of the
postings says that cas
>>
At -140 dBm and 250 Hz noise bandwidth, the system would require a 1 dB
noise figure front end. That's about 35 deg K noise temperature.
>>>
Tom is as usual 100% right, the RX system gain should be near 1 dB, it means
the preamp at 1.8 MHz should be .5 dB NF the input filter and the feed
, September 06, 2015 5:53 PM
To: k...@myfairpoint.net; topband@contesting.com
Subject: Re: Topband: Waller Flag Question
Bruce wrote on Sept 6.
Snip <
Check it out
http://www.qsl.net/k4fk/presentations/WF-receiver-antennas-SFDXAs.pdf >
Bruce, ref to the link above there is a gap in the &q
Thank you, JC:
I don't know where this coming from ,but the gain you need for a VWF
modest
size is 20db for vertical polarization and for horizontal HWF you need
40db
on 160m, on 80m divide this by 2, you need only 20 dB and on 40m 10 dB a
NORTON preamp is enough. All situations you need a
"" A similar observation was made 20 years ago by Brian Beezley, K6STI, in a
QST article titled "A Receiving Antenna that Rejects Local Noise"
(September, 1995, page 33): I've been looking around for something that
might work better than my present antenna, and I see good reports about the
Maybe his secret is a preamp cooled with liquid helium! ;-)
Seriously, there are preamps operating at 70 degrees F (for example) that
have less than a 1 dB NF at VHF. They are usually mounted at the feedpoint
of a high gain array, because of feedline loss.
Today, I have the type of terrible cold
On Sun,9/6/2015 4:31 PM, Tom W8JI wrote:
Thanks for the insights. I have no doubt the theory is correct. My
sense, though, is that in the denser suburbs, we live in a "fog" of
local radio noise, generated by the scores of digital and other
devices that surround us.
The sad thing is that
Bruce wrote on Sept 6.
Snip <
Check it out
http://www.qsl.net/k4fk/presentations/WF-receiver-antennas-SFDXAs.pdf >
Bruce, ref to the link above there is a gap in the "History of the Flag
Antenna" The earliest fef. to the Terminate loop I have found is in Keen’s
Wireless Direction Finding
Thanks for the insights. I have no doubt the theory is correct. My sense,
though, is that in the denser suburbs, we live in a "fog" of local radio
noise, generated by the scores of digital and other devices that surround
us. A similar observation was made 20 years ago by Brian Beezley,
It can be done. JC, N4IS has been doing it and has the DX contacts that
most can not hear.. The proof as they say "is in the pudding" He uses
balanced twisted pair feed lines with pre-amps, and other noise
reduction techniques..
Check it out
The on-line materials about Waller Flags says that a modest size WF would need
about 40 dB of gain to boost the signal to a usable level. One of the postings
says that cascading two preamps of 20 dB each seems to add extra noise, and
they talk about developmental work being done on a single
Art Delibert wrote on Set. 6
snip would need about 40 dB of gain to boost the signal to a usable level. One
of the postings says that cascading two preamps of 20 dB each seems to add
extra noise, and they talk about developmental work being done on a single
preamp of 40 dB.
Is there now
The on-line materials about Waller Flags says that a modest size WF would
need about 40 dB of gain to boost the signal to a usable level. One of
the postings says that cascading two preamps of 20 dB each seems to add
extra noise, and they talk about developmental work being done on a single
23 matches
Mail list logo
