开云体育

The QRP Labs SI5351 VFO kit may be what you are looking for. The latest version will output I and Q for phasing rigs.?

Need to build, or buy a kit, of an IQ Quadrature out test oscillator. Haven’t seen anything around!?

Thanks

Hi

Just seen your message so I thought I would chirp in with a little info.

I am presuming when you refer to the "fundamental squarer" you are talking about its use in a H-Mode mixer?

My Irwell HF multi-mode transceiver project contains two H-Mode mixers with fundamental squarer circuits. In my mixers I used three ultra high speed NC7SZ04M5X IC's but you could also use a single 74AC04 to do the job.

It is my understanding that a divide by two squarer is not necessary if the switches being driven do not require a phase difference.

I will probably post full details of my H-Mode Mixer's in the near future once I have carried out further test, for now the mixers are performing well in the receiver stages but I have yet to try them in transmit.

Regards

Andy de G6LBQ

Hi Paul

Great to hear that you have completed a scratch build of my MKll BitX multi-band transceiver.

I have not seen or experienced the chirp you mentioned when going from RX to TX so I suspect the problem is associated with the TDA2003 amplifier stage.

As standard the MKll multi-band exciter has an LM380-8 as the final audio output stage and I chose this as my experiences with the LM386 have not been great!

Both the original BitX and my multi-band effort do suffer with speaker "thud" when going from RX to TX, in my circuit Q11 in the audio stage does help reduce the thud to an acceptable level but there is still room for improvement and one day I may look at this again.

When working correctly with everything aligned the receive performance is excellent considering its simplicity. The AGC makes a huge difference over the standard BitX without an AGC and the transmit audio is greatly improved with the op-amp and its associated filtering.

Keep us posted on your progress and it is great to hear that you are enjoying the project.

Regards & 73

Andy de G6LBQ

Can the 74AC74 be configured as a fundamental squarer, ?( no with need to divide) with 180 and 0 out?

Thanks for replying Ken. I'm on [email protected] and have seen the series FET switch and kit. I'll look into it.? I have a hunch that it might be the big electrolytics in the TDA2003 audio amp, I will test out this theory first.??

When this nice little rig is working sufficiently well I will write up a blog post and post a link here. The G6LBQ design is a fine variant on the Bitx pattern that makes it just right for my interests and purposes.?

73 de VK3HN.??

Hi again

My homebrew (scratch built) G6LBQ BiTx txcvr is assembled and in debug stage. Overall, I'm pleased with the results, the Rx has lots of gain and the AGC works well.? I routinely enjoy listening to US amateurs on 7.150 to 7.170 in my evenings here (VK3), despite the quite poor band conditions being experienced around the world right now.??

My build is:

- Arduino Nano/LCD/si5351 with a single broadbanded 2n2222 buffer/amp for both VFO and BFO
- TDA2003 replaces LM386
- IF is 9MHz
- 5 (not 6) crystals in the filter, capacitors are 68p and 82p, couplings are the original 100p, the filter is a little bassy so I will experiment with some smaller values to move the passband a bit higher
- PA uses one RD16HHF1 (not two in push pull) in a standard QRP 5W PA circuit
- For T/R switching, one digital input on the Nano senses the PTT switch going low, then raises another digital output, which pulls in the two relays on the PA board; one relay has a set of contacts that switch 12v between the low level stages of the Rx and Tx.??
??
Otherwise it is exactly as per the MkII circuit diagram.? The build is on a hand drawn PCB that is mostly ground plane, and with surface mount parts.? The Exciter board is bolted tightly to an aluminium case lid. The MC1350 took a few tries to get aligned, it was distorting until I got the tuned circuit on its output pins close to resonant, but now the receiver sounds clean and shows no signs of instability.??

Back on the AGC, mine is not quite adjusted right yet, the no-signal voltage is too low, so when you turn on the AGC the receiver noise level drops too far. The AGC action is good on strong signals.??

The curious thing is that when I press PTT there is a sharp chirp of audio generated.? It is as loud as the subsequent spoken voice, starts off about 1khz and drops quickly, lasting about 100-200mS.? It is prominent enough that it will draw comments from other stations in a QSO.? It? suggests an electrolytic capacitor charging/discharging.? I removed the 50uF supply filter cap on the mic amp -- no difference.? I reduced the 10u in series with the mic amp hot input to 2u, no change.?
?
If I manually switch the rig to Tx it still happens, so it might have something to do with power switching between Rx and Tx.?
?
Just wondering if anyone has seen this.?

The Tx is working too, but becomes unstable with the PA bias above about 400mA, so it needs better shielding, I'll spend some quality workshop time with hacksaw file and PCB stock to create some compartments inside the box.? ?

73 Paul VK3HN.? ?

Hello Dave,

I have been working on one of these myself, I'm interested in what
VFO you had planed on using?

73, Rick - K6ZWB

My Almost completed BitX transceiver that I brought back from the USA with me is still sitting in the loft. I ?will never get time to complete it so I am offering it as a package for someone else to apply the final touches. The package includes the following:-

Built and aligned Exciter Module

Built and aligned Lowpass filter Module

Built and aligned Bandpass filter Module

Built PA Module with heatsink

Exciter dc switching relay board

Unopened VFO kit

Custom Case

Plugs / pins for exciter connectors (currently wires soldered directly)

All modules have SMA RF connectors, matching interconnecting leads included (see photos)

It has had qsos in the past with external VFO and TR7 amp, but needs controls wiring and new meter fitting (the old one didnt survive the trip home!)

Photos are at http://g4fre.com/sale.htm

Asking ?200 plus shipping to mainland UK?

Email me if interested

Dave

G4FRE

Andy and the group,

One more question for anyone using an si5351 clock as the VFO in a G6LBQ transceiver -- what buffering/amplification stage are you using between the si5351 clock and the ADE1 L7 mixer??

A barefoot si5351 clock is not sufficient in my experience to generate +7dBm. I've used a 74HC04 squarer followed by a 10dB pad, but hoping to avoid this complexity this time. A simple 1 or 2 transistor buffer should suffice. There are circuits I can lift from other sources but it's always best to hear other makers' experience.?

73 Paul VK3HN.?

Thanks for your comments Andy.

I'll plan to use 100pF caps for CP1-5 and Cs in a 9MHz 6 crystal filter.

I'll heatsink the RD16HHF1 driver with a common finned heatsink on top of the board.

One further question, I've got experience with IRF510s in QRP PAs but not RD16HHF1s. How rugged are the RD16HHF1s? will they tolerate higher SWR? Open circuit?? While you never? expect to treat a QRP PA badly it happens when in a rush, on a summit, or portable! The IRF510s are not overly rugged in my experience at 12-15V but cheap to replace.??

And I'll report as this project progresses. Also looking forward to seeing your design for IRWELL.

73 Paul VK3HN.??
.

Adrian

Thanks for the offer, but I've custom built a compact aluminium chassis for this rig, it is to be a 2 bander for SOTA and walking.? Thanks for the offer.

73 Paul VK3HN.? ?

Hi Paul

I spotted this post on the G6LBQ group.

I have some MKII boards that have not been populated. If you are
interested (and I can find them!) you can have them at cost price plus
shipping ?

I definitely have the main boards and possibly the filter boards.

Adrian M1LCR

Hi Paul

Let me try and answer your questions:

1. The Mk II instruction manual refers to T1, an FT50-43 impedance matching transformer on the output of the xtal IF filter, but this is missing from the MkII exciter circuit diagram.? I assume T1 was replaced by the 200 ohm resistor between Cs and the 10nF on pin 4 of the MC1350P. >>>> You can use either method transformer or resistor which ever you prefer, I found no difference with regards to performance its one less coil to wind :)
   
   
2. I plan to use a 9MHz 6-pole crystal filter for SSB, around 2.4kHz .? I found references in this group to CP1-5 (initially 68pF, then 100pF).? This range seems typical for such a filter.? I have run up Dishal but the filter topology it assumes for 6 crystals is not a straight ladder, it is an asymmetrical arrangement with a central C.? I'll start with 100pFs and see how it sounds. >>>> The capacitor values were chosen pending which xtals were used when I made the filter kits up, I used a VNA to spec my xtals and aimed for xtals within a 40 Hertz range.
   
   
3. There are three capacitors in series with the crystal filter, Cs, for which I cannot find a value. >>>> The value of CS capacitors is the same as those for CP
   
   
4. I plan to heatsink the two RD16HHF1 PA FETs against the aluminium case.? No insulation kits required as the devices tab is its source.? Does the RD16HHF1 driver need heatsinking?? If so, can it be bolted to a small finned heatsink on the board, or does it need to be mounted flat against the aluminium case as well?? >>>> The driver transistor only requires a push on TO-5 or TO-39 heatsink, this is what I have used: https://uk.rs-online.com/web/p/heatsinks/0401548/
   
   
5. Finally, I have a LiPO 4S pack which produces 14.8 V fully charged, and a LiFePO 4 pack which has the potential to produce 14.4 v fully charged. I use these packs with QRP IRF510 PAs and I get a bit extra juice.? Will these slightly higher voltages stress the Mk II PA in any way? >>>>? The RD16HHF1 has an absolute max rating on the Drain to Source of 50 Volt according to the spec sheet so I do not think 14.4 Volt is going to do any harm, just be aware that the higher voltage may affect the linearity.

Any further questions feel free to ask!

Regards

Andy de G6LBQ