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I just got to retest inserting a 1 KHz
tone and also with speech. I tested on 21 MHz and drove the signal
until I got my full output, 7 watts. The spurs were around -46 dB.
With my equipment, I need to eyeball it, it doesn't make
measurements, its a 40+year old analyzer I bought in the 70s. IT
seems my rig is compliant, but not by a huge amount.
On 10 meters I get 4.5 watts. I have done a lot of simulations
using IRF510s and believe that I can get them to produce 10 watts
on 10 meters. I am documenting the work, and will share it later.
Oh, my power supply is 12 volts, not 13.5.
On 6/4/2018 5:20 PM, Arv Evans wrote:
is correct that things are much cleaner when using CW.
my tests I inserted 1KHz at variable levels and adjusted the
audio level for
cleanest RF on the oscilloscope. Then I performed a frequency
sweep to look for
As long as the microphone port audio input is below 45
millivolts the spurs seem
be down at least 50db, but can be pushed even further down by
reducing the audio
to around 32 millivolts. This seems to be where oscilloscope
peak-to-peak RF level
is about the same as when using CW mode.
I could not duplicate this using an averaging type RF
voltmeter as the signal level detector.
is interesting to vary the microphone port input frequency and
watch each spur to see
it moves up or down. This could be an aid in figuring out how
each spur is being
On Mon, Jun 4, 2018 at 10:32 AM Howard Fidel <sonic1@...
I just got an explanation from Allison, which I will
confirm later. I measured the spurs in CW which I thought
was a side tone, but isn't. I need to retest with actual
On 6/4/2018 12:21 PM, Arv Evans wrote:
seeing about the same.
On Mon, Jun 4, 2018 at 10:18 AM Howard
When properly driven, I see the spurs almost at
On 6/4/2018 11:37 AM, Arv Evans wrote:
uBITX does actually work on 15M, 12M, and 10M
(and yes it does work on 11M as
by the number of CB'ers who have purchased
it). Power output is much lower
the higher bands, but is still enough to make
QRP contacts. Just do not try to increase
output on upper bands by adding microphone
gain. Too much microphone audio
cause spurs, distortion, and QRM.
To keep the price
down, I think hfsignals may as well continue
to use the 45mhz filter.
Perhaps claim 80m through 17m, beyond that is
experimental, disable 15m,12m, and 10m
in the stock firmware. Different transistors
for more consistent gain should be considered.
However, if we can instrument drive level into
the mixers, sounds like we may be able to have
a clean signal on up to 30mhz. Perhaps
replace transistors to get consistent gain
through the 45mhz IF
and the Q90 stage, then monitor the top of RV1
with a diode RF probe into a Nano analog pin.
Better yet, add another 10dB of gain after the
mixers so the IRF510's show trouble (much more
long before the mixers do. So maybe add an
extra gain stage between Q90 and RV1,
existing rigs could easily patch this in with
If we do decide to go to 70mhz and beyond for
that first IF, there are viable filters
In this post: https://groups.io/g/BITX20/message/33203
Farhan explains that the 45mhz filter must be
narrow enough to reject signals 2 mhz away
Here's the filters on Mouser that are between
70 and 90 mhz, and have a bandwidth of less
The PX1002 from Murata looks good to me,
center frequency of 86.85mhz.
25khz wide, 3dB insertion loss, over 60dB of
rejection at 1mhz out,
datasheet shows how to use it in 50 ohm
Not exactly cheap at $12 single unit, $6 if
buying hundreds from Mouser.
The similar PX1004 at 82.2mhz is harder to
get, especially in low quantities,
but might be preferred as it allows a lower
To operate at 30mhz with an 86.85mhz first IF,
the vfo should be 86.85+30 = 116.85mhz.
The Si5351's internal vco is spec'd to a max
of 900mhz, and our fractional output dividers
can divide down
to a minimum of 8.0, so 900/8=112.5mhz max
using the current si5351bx routines with the
vco moved to 900mhz.
Hans, G0UPL, has found that the vco can be
pressed to go much higher, beyond 1100mhz,
so we could just cheat on that, perhaps 935mhz
for the vco giving 935/8 = 116.875mhz max.
I'd try that first.
The other possibility is to use the second
Si5351 internal vco with fractional pll
feedback and an
integer output divider on clk1, giving fine
grained frequency control up to 200mhz
(290mhz, according to Hans).
This second method would roughly double the
size of the si5351bx routines, but that's not
a major hit.
The other two si5351 outputs would continue to
use the first vco, and be restricted to
If using the equations of post https://groups.io/g/BITX20/message/44278
the only needed change to the uBitx code
outside the Si5351bx routines would be to
f45c = 44995000; // center of 45mhz
f45c = 86850000; // center of 87mhz
The filter and 50 ohm matching networks
could be on a very small PC board
glued to the back of the uBitx main board.
This daughterboard could include a new BiDi
amp with appropriate transistors.
If the uBitx mixers are problematic at
86.85mhz, then perhaps a couple ADE-1's also,
replacing everything from T2 to T4 inclusive.
Parts cost of around $10 if building hundreds,
$15 bucks if adding the two ADE-1's.
Then everybody will get fixated on making the
uBitx work on 6 meters
and we get to do this all over again.
On Sun, Jun 3, 2018 at 03:44 pm,
Its not a drop in. The filter
would likely be hard to find and costly or
for a one off salvage from
an old junker commercial radio.
I think Kenwood radios used a 63mhz filter
or maybe ICOM. so lets do a thought
experiment on what needs to be done.
The filter would need to be matched and like
data for it will require experimental
The T30-2 toroids could be reused and
rewould and the cap for the L-networks
as needed. The entire string of 3904s [all
6 of them] in the 45mhz section would have
to be some thing like 2n2369, or better
Then the firmware has to be revised as the
first lo needs to be higher to start maybe
65mhz and go up from there.
So yes it can be done. I don't have such a
part so thats ruled out. So for a one off
maybe, doesn't help everyone though. and
even if the filter was not too expensive
thats a lot of SMT and through hole work
plus a new firmware. At the production
level it could add significant cost and
interrupt the product flow as you have all
material in place and likely paid for.
Right now the most feasible option is
bandpass filters and switching. Cost wise
parts are cheap is SMT inductors are used.
The trick there is drop in and play no