EMRFD Message Archive 426
Message Date From Subject 426 2007-02-03 06:03:34 Jim Miller Playing around with RF receive amps
The 2n5109 seems to have been around a long time in this role and I'm going
to order a few.
Are there any others which are newer that I should consider as well?
Especially ones which surface mount?
73
jim ab3cv427 2007-02-03 07:02:28 larry allen Re: Playing around with RF receive amps
receiver, might I suggest that you do some research into better antennas
and transmission lines first....You can get more signal, to your receiver,
if you decrease the loss of the antenna/transmission line system....
Or put the preamp where you antenna connects to your tranmission line and
use a separate antenna for your receiver and transmitter....
Larry ve3fxq
----- Original Message -----
428 2007-02-03 07:08:57 Jim Miller Re: Playing around with RF receive amps
around with antennas separately.
73
jim ab3cv429 2007-02-03 08:35:49 Luiz Amaral Re: Playing around with RF receive amps
Luiz - PY1LL
----- Original Message -----
430 2007-02-03 11:04:53 Jim Kortge Re: Playing around with RF receive amps
> I'm going to breadboard some receive preamps just to do some learning.I like the BF199. 700 MHz Ft and dirt cheap from Mouser and others.
>
> The 2n5109 seems to have been around a long time in this role and I'm going
> to order a few.
>
> Are there any others which are newer that I should consider as well?
> Especially ones which surface mount?
72,
Jim, K8IQY431 2007-02-03 18:12:34 Jim Miller Re: Playing around with RF receive amps
I looked at the Fairchildsemi datasheet for the BF199 and didn't see any
noise figure specified.
Any ideas?
73
jim ab3cv432 2007-02-03 18:13:39 Jim Miller Re: Playing around with RF receive amps
Who is the manufacturer for these? I looked at NXP (spinoff of Philips) and
they have similar part numbers but not these in their RF line.
73
jim ab3cv
----- Original Message -----
433 2007-02-04 03:00:36 Luiz Amaral Re: Playing around with RF receive amps
Luiz - PY1LL
----- Original Message -----
434 2007-02-04 03:05:56 Luiz Amaral Re: Playing around with RF receive amps
conditions:
IC = 40 mAdc, VCE = 10 Vdc, RS = 50 Ohm and f = 35 MHz
Luiz - PY1LL
----- Original Message -----
435 2007-02-04 04:45:40 Jim Miller Re: Playing around with RF receive amps
Motorola exited the semiconductor business by spinning it out to a separate
entity, Freescale Semiconductor, in 2004. If you do a search on FreeScales's
website you find BFR90 and BFR91 listed as obsolete with a last time buy
back in 1999 when they were still part of Motorola. FreeScales lists
Advanced Power Technology as a alternate supplier of near compatible
replacements.
If you then go to Advance Power Technology website you find that they are
now Microsemi. (starting to feel like a shell game at a carnival...)
MicroSemi does have the parts you and FreeScale reference but they have very
limited distribution, at least in the US, and no way to buy parts online.
Their one distributor, Richardson Electronics (never heard of them...) has
only 177 of the BFR91 and none of the BFR90 available and no online
ordering.
None of the above list BF199 at all.
The result is that the parts mentioned aren't really current anymore and I'd
rather focus my efforts on current parts rather than ones from surplus
suppliers. I suspect what is happening is that higher levels of integration
along with a primary focus on volume markets for wireless at 900Mhz and
above (cell phones, wireless lan, etc.) is diminishing the interest and
market for discrete products for HF use.
BTW, Philips likewise spunout their semi operation to NXP who has also
dropped a number of parts...
I guess I'm going just play with the 2N5109 for now and continue my search
later.
I'd appreciate any further finds however!
thanks and 73
jim436 2007-02-04 05:48:08 w4zcb77 Re: Playing around with RF receive amps
> >
> I guess I'm going just play with the 2N5109 for now and continue
> later.Snipped a bunch.
>
> I'd appreciate any further finds however!
>
> thanks and 73
>
> jim
Well Jim, I could make a recommendation for the use of the circuit
shown in EMRFD fig. 6.94.
This feedback amplifier, (and I've probably built 15-20 of them) due
to its feedback, is very reproduceable. The same feedback,
establishes its input impedance close to 50 Ohms and yields a noise
figure of 1.25-1.5 dB. The output is not in the feedback loop, but
with most J-310's, it runs in the order of 50 Ohms and the reverse
gain with neutralization exceeds -60 dB. Input Ip3 measures 24-26
dBm, gain well established around 12.5 dB and have I mentioned that
the last time I bought J-310's, they were $0.18 each in 100 quantity?
(Readily available from many suppliers, heck, for a SASE, I'd even
part with enough for a couple amps.)
Regards
W4ZCB
>437 2007-02-04 06:14:40 Jim Miller Re: Playing around with RF receive amps
After making that last post I went to investigate JFETs and had already put
2N4416 and J310 types on my Digikey order sheet.
Thanks for the pointer back to EMRFD. That was my next stop to figuring out
what I could do with the fets.
Now if I can learn enough about 3dsMax to stay ahead of my daughter so I can
help her with her homework ...then I can get back to hamstuff!
73
jim ab3cv438 2007-02-04 23:55:03 jr_dakota Re: Playing around with RF receive amps
2N5109, I'm especially fond of the 2SC1253 because Dan's Small Parts
has them for a $1.50
In a classic feedback design you have a very good preamp, if you need
a little better use one in a Nort439 2007-02-05 06:59:18 Giancarlo Re: Playing around with RF receive amps 441 2007-02-05 17:34:24 Mike Brainard Re: Playing around with RF receive amps
> Especially ones which surface mount?
>
MOSFETS in lots of 100 pieces from time to time on ebay. He has also
been known to deal directly on some that have fallen out of the anti-
static packaging tape. Price is right either way. See W7ZOI website for
a 6 meter example application.442 2007-02-05 20:56:03 Wes Hayward Re: Playing around with RF receive amps
Your question regarding the RF amplifier parts seems to have caught
the imagination of the group. It is always fun to build up and
experiment with such circuits.
One SMT part that I have had good luck with is the MRX5943. It is a
SOT-89 and I think that it was made by Motorola. I found some in
local surplus, but it is not a common thing. It seems to be a SMT
variation on the 2N5943, which is much like a 2N5109.
A more practical new part is from NEC, the NE46134. This is also a
SOT-89 packaged part with an F-t up around 5 GHz with 50 mA. They
are found in DigiKey's latest catalog, TO71, page 440. I used one
in a linear chain for 50 MHz. It was a feedback amplifier with an
output of +15 dBm or so. It was running Vce=9 and Ie=40 mA with 50
Ohms at both input and output. The feedback was 270 Ohms in
parallel (AC) with a 2.7K bias R while the emitter had 12 Ohms
paralleled (AC) with a 51 Ohm bias element. S21 was 10 or 11 dB.
I purposefully kept it that low. The performance should be
virtually unchanged at 144 MHz and nearly as high at 432 MHz. The
cost is under $2. I didn't measure NF in the amplifier I built.
There are a pile of other NEC bipolar parts listed in the catalog in
smaller packages. My experience with NEC has been nothing but
positive and I would guess that these low power parts would be
outstanding. They are mostly priced under a buck in singles.
I think that specs for these parts are found on line.
We tend to look for really hot (high F-t) parts, even when working
down at HF. While that may be justified if we are going for the
ultimate in NF, it may not make a lot of sense if we don't have the
parts on hand, or severe requirements. I used a pair of parallel
2N3904s as a feedback amp in a Chapter 6 receiver and they worked
great. The IMD performance does not depend much443 2007-02-05 22:41:09 jr_dakota Re: Playing around with RF receive amps
shipping, sure beats $3-4 for through hole ones .... What I've been
doing with them is take my dremel with a cutoff wheel and make a bunch
of 'X's on some PCB scraps and then I take my manhattan pad punch but
use the next size larger punch than normal, center it on the 'X' and
punch it out ... This leaves me a pad with the copper cut into 4
slices and I mount the MOSFET on it .... I usually make up 10-12 at a
time and when I need a dual gate MOSFET all I have to do is glue the
MOSFET/pad combination to the PCB and build off of it .... I store
them in one of those plastic boxes you get samples in and sandwich
them between two pieces of antistatic foam .... I even took one, added
four legs from old component leads and dropped it into a circuit that
had a blown 3N211 and resurrected a little varactor tuned
preselector/variable gain RF preamp for my R2 Pro until I get a
multiband soluti445 2007-02-06 04:57:40 Jim Miller Re: Playing around with RF receive amps
Thanks for the pointer to the NEC device. I'll give it a try.
I don't mind using "mature" parts or getting creative with '3904's but I
wanted to try some appropriate SMT parts that represented current state of
the art in transistors. The NECs look like they will fit that desire.
73
jim ab3cv481 2007-02-16 09:40:11 Bruno Re: Playing around with RF receive amps 482 2007-02-16 10:06:05 kd5nwa Re: Playing around with RF receive amps
At 11:38 AM 2/16/2007, you wrote:
>484 2007-02-20 09:39:39 Bruno Re: Playing around with RF receive amps 485 2007-02-20 09:56:28 Jim Miller Re: Playing around with RF receive amps
73
jim ab3cv486 2007-02-21 05:14:29 Bruno Re: Playing around with RF receive amps 487 2007-02-21 05:25:43 Bruno Re: Playing around with RF receive amps