Date   
Re: DSB transceiver for Digital mode

Ron Stone
 

Adam,

Glad to see that you're going forward with 20 meter version sooner rather than later.  Are you getting customized crystals for 14.074 Mhz or is it anothet frequency crystal that has to be pulled a bit?  If so what frequency is it for 20 mtrs?  Thanks.

Ron (ka3j)

Re: DSB transceiver for Digital mode

Adam Rong
 

Ron,

I use 14.070MHz HC-49U crystals and pull them high about 4kHz. The crystals were customized before and I have enough stock. They work perfectly for 14.074MHz.

Thanks,
Adam

Re: DSB transceiver for Digital mode

Adam Rong
 

Folks,

This is a bit history for D4D: A simple QRP transceiver kit for FT8.

D4D stands for DSB transceiver for Digital modes. It is a Double Sided Band transceiver kit designed for digital modes, especially for FT8. If you have chance to try FT8, you will be amazed by the strong decoding capability due to the communication protocol, digital signal processing and software. I still remember clearly a YouTube video by W6LG who communicated with a bulb. I started to think how much the transceiver could be simplified if you have a moderate antenna like a full sized dipole or EFHW instead of a bulb. A DSB transceiver is much simpler than a SSB transceiver, however it was never used for FT8 as far as I know. I did some experiments on my Choc perf board, a specially designed perf board for RF circuit experiments. I started with a direct conversion receiver for FT8 and it worked okay. Then I built a DSB transmitter and the transmitted signal can be decoded. By referring to the DSB designs of AA7EE, VK3YE and ZL2BMI, I combined them using only one NE602 and a PTT switch and it gave me success to make a few FT8 QSO’s. Personally I really enjoyed it because a manual PTT switch will save power consumption and circuit complexity, but you will need to well sync with computer, although it was not really a problem for me. Per request from a few hams, I found a VOX control circuit and modify the hold time to be compatible with FT8, and I put them together and made a few improvements on the signal purity and frequency stability, and it finally became our D4D. Do we have to worry about the unwanted Lower Side Band? Maybe, but for a transmitter of 1-watt, it is not really a big problem. Is it just a toy for a transmitter of 1-watt and only half of the power will be effective? Not really, as I can easily make a few QSO’s as far as 1500 miles range for 40-meter band.

Thanks,
Adam


在 2019年4月26日,上午9:05,Adam Rong via Groups.Io <rongxh@...> 写道:

Ron,

I use 14.070MHz HC-49U crystals and pull them high about 4kHz. The crystals were customized before and I have enough stock. They work perfectly for 14.074MHz.

Thanks,
Adam

Re: DSB transceiver for Digital mode

Adam Rong
 

Folks,

I have put together a final version and it worked perfectly. Now I accept order for beta testing.

 I will ship 3 kits of 7074 by May 6. If you join beta testing, you will need to keep secret before Hamvention debut. You will have time and equipment to build and test the kit and publish a test report. If you have a popular YouTube account or web site, please let me know so you will have priority. Please contact me offline.

The MP version will be shipped on May 20.

Thanks,
Adam

Re: FT8 HT

Adam Rong
 

In case you are following this thread, please see this:
https://groups.io/g/crkits/topic/31005901#2560

Now the idea comes true.

Thanks,
Adam

Re: DSB transceiver for Digital mode

Adam Rong
 

Folks,

Well, it was leaked by qrper.com. Check it out for now, although some data might be modified later.

Thanks,
Adam

在 2019年5月2日,上午5:19,Adam Rong via Groups.Io <rongxh@...> 写道:

Folks,

I have put together a final version and it worked perfectly. Now I accept order for beta testing.

 I will ship 3 kits of 7074 by May 6. If you join beta testing, you will need to keep secret before Hamvention debut. You will have time and equipment to build and test the kit and publish a test report. If you have a popular YouTube account or web site, please let me know so you will have priority. Please contact me offline.

The MP version will be shipped on May 20.

Thanks,
Adam

Stay tuned for more analog kits

Adam Rong
 

Folks,

I just realized that FT8 is so popular that someone loves it and someone hates it. However I hope in here both digital and analog kits can coexist. D4D actually is an all analog transceiver without MCU, DSP or SDR. It can used for FT8 and FT4 but it can also been used for voice transmission as long as the input is big enough to drive the VOX.

Currently we are offering HT-1A CW dual bander which is a cool radio kit. And we also offer R3500D ARDF 80m receiver. Both are analog radios. I discussed with team and we are going to release the successor of KN-Q7A. We don’t have timetable yet but we think it is a good direction to go. I also like to introduce my minimalist NE602 receiver as a kit. It was kitted based on my Choc perf board for Japan and I want to make a PCB and find a case, so it could be used for a club project. Stay tuned although we are discussing a little bit more about FT8 and D4D these days.

Thanks,
Adam

New file uploaded to crkits@groups.io

crkits@groups.io Notification <crkits+notification@...>
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the crkits@groups.io group.

File: d4dpartlist20190504.xls

Uploaded By: Adam Rong

Description:
D4D part list for 40m and 20m

You can access this file at the URL:
https://groups.io/g/crkits/files/D4D%20Kit%20Documentations/d4dpartlist20190504.xls

Cheers,
The Groups.io Team

Can R3500 work on 8.4V?

YT9TP - Pedja
 

I would like to use LiPo battery with R3500. I suppose I have to use 2S cells which means maximum voltage could be 8.4V.

Is that to much for this rig?

Re: Can R3500 work on 8.4V?

Adam Rong
 

Judging from the schematic, I don't see big problem.

Thanks,
Adam

在 2019年5月5日,下午7:01,YT9TP - Pedja via Groups.Io <yt9tp=uzice.net@groups.io> 写道:

I would like to use LiPo battery with R3500. I suppose I have to use 2S cells which means maximum voltage could be 8.4V.

Is that to much for this rig?


Re: DSB transceiver for Digital mode

Adam Rong
 

Folks,

I have decided on all the key parts, and purchased most of them. The relay reliability is very important, so I have chosen Zettler, the same brand used in Elecraft K2 kit I have purchased before. The ferrite FT37-43 is produced by Fair-Rite and purchased from Mouser. All the capacitors under 1uF is produced by Torch, the top brand in China.

I will announce the product via my web site in the May 11-12 weekend and start to take order. The first order will be shipped no later than May 20. If you wish to get some assembled kits, please let me know ahead of time.

Thanks,
Adam

Re: DSB transceiver for Digital mode

Ron Stone
 

Adam,

Glad to hear about your progress.  Just a few questions.

- What are the dimensions of the PCB (or case)?

- Do you recommend using the heating resistor especially on the 20 meter version?  Was the stability still ok without it?  How much did stability improve with the resistor?

-  Did you experiment using a higher gain LM386 or other audio amp instead of the single transistor audio amp circuit that you're using?  If you did, was there much difference in performance?

Thanks again for all your efforts!

73,

Ron (KA3J)

Re: DSB transceiver for Digital mode

Adam Rong
 

Ron,

Thanks for the questions.

1. The PCB size is around 100x64.
2. The heating resistor is recommended for 14MHz. It is really a balance between short term and long term but I see overall improvement. This idea is very rare so I need some more experimentation from you guys.
3. The real concern is not sensitivity but SNR. Since the output impedance is several hundred ohms, by using one transistor, the signal is big enough to give 40-50dB, already bigger than recommend 30dB. My previous version was LM386 and I don’t see much difference. However I have to say that the receiver SNR report  is noticeably worse than big radios. I can easily improve receiver itself but considering transceiver overall, I have to sacrifice a bit. The receiver performance is reasonable to match one-watt DSB transmission. You have to balance.

Thanks,
Adam

在 2019年5月6日,上午6:24,Ron Stone <rsstone2@...> 写道:

Adam,

Glad to hear about your progress.  Just a few questions.

- What are the dimensions of the PCB (or case)?

- Do you recommend using the heating resistor especially on the 20 meter version?  Was the stability still ok without it?  How much did stability improve with the resistor?

-  Did you experiment using a higher gain LM386 or other audio amp instead of the single transistor audio amp circuit that you're using?  If you did, was there much difference in performance?

Thanks again for all your efforts!

73,

Ron (KA3J)

Re: DSB transceiver for Digital mode

Ron Stone
 

Adam,

Thanks much for your responses.

When making comparisons with a big rig, how much worse was the received SNR report?  With the little rig, would you say it was 5 dB, 10 dB, or 15 dB worse?  Also, how many fewer decodes can we expect - 25% less, 50% less?   

Since I'm planning to put the rig in an enclosure with a Raspberry Pi, there is going to be plenty of heat around.  So once things warm up, do you think this would help with longer-term frequency stability and make it unnecessary to use the heating resistor?   Of course, I'll be more than happy to experiment and share my results.  

73,

Ron (KA3J)

Re: DSB transceiver for Digital mode

Adam Rong
 

Ron,

SNR is 5-10 dB worse. However, I found that I only can make QSO with radios of -15dB SNR or better, so I think this is not a problem. Same as QRP communication, you have bigger chance to QSO with bigger signal. You may have interest to hear more signals even you don’t have chance to make QSO, but if I improve the SNR, I have to sacrifice RF output power to avoid self-oscillating. This is the limitation of using only one NE602 for TX and RX, and I chose to sacrifice RX performance to make the transceiver more balanced.

Heating is a complex question. It is documented that if the ambient temperature is around 50 C, the thermal drift of an AT cut crystal is minimal. Adding heating resistor is just to complete the heating progress in short time. There is just another way to help you if you really need help, especially on 20m band in which specific percentage of drift will cause bigger amount of drift in Hz. Also the heating power is only available during RX, so it is kind of compensation during RX.

Thanks,
Adam

在 2019年5月7日,上午2:10,Ron Stone <rsstone2@...> 写道:

Adam,

Thanks much for your responses.

When making comparisons with a big rig, how much worse was the received SNR report?  With the little rig, would you say it was 5 dB, 10 dB, or 15 dB worse?  Also, how many fewer decodes can we expect - 25% less, 50% less?   

Since I'm planning to put the rig in an enclosure with a Raspberry Pi, there is going to be plenty of heat around.  So once things warm up, do you think this would help with longer-term frequency stability and make it unnecessary to use the heating resistor?   Of course, I'll be more than happy to experiment and share my results.  

73,

Ron (KA3J)

D4D: Ready to Take Order

Adam Rong
 

Folks,

I start to take email order now. The introductory price is 39 USD for kit including shipping to worldwide. As in the introductory period, you will get audio cable options for free. The earliest possible shipment date is now improved to May 13.

You can directly PayPal to rongxh@... and let me know 40m or 20m (80m not ready yet). I will ship based on the sequence of receiving your payment. I may delay shipment for one week or two due to workload.

This is the spec so far:

Summary: Crystal controlled single frequency DSB transceiver for 20m (14.074MHz), 40m (7.074MHz) or 80m (3.573MHz), other frequencies could be added per request
Power supply: 10-14V DC regulated power supply or battery pack, 12V is recommended, center positive, reverse polarity protection available
Current consumption in RX: about 15mA at 12V
Current consumption in TX: about 300mA at 12V
RF output: about 1W for 40m band at 12V, and a bit less for 20m band
Spurious suppression: no worse than -50dBc
Antenna connector: BNC connector, 50 ohm
Audio in connector: 3.5mm mono, at least 600mV to activate VOX, connects to headphone connector at PC sound card, no dedicated PTT connector is required
Audio out connector: 3.5mm mono, connects to microphone connector at PC sound card
Amber LED: TX status
Green LED: RX status
Frequency accuracy: -600 Hz ~ + 200 Hz
Frequency stability: Okay for FT8 mode per test. If the optional heater resistor R20* is added, after warm up, long term frequency stability in 10 min will be improved at the cost of acceptable short term frequency stability sacrifice in 30 sec.

Thanks,
Adam

Re: D4D: Ready to Take Order

maximilien971
 

Hello Adam
Very interesting!

Sorry if you still talk about it,  is there the case I have seen in the pics section?

73
Patrick
F6GWE

Re: D4D: Ready to Take Order

Adam Rong
 

Patrick,

The beautiful black metal case is included in the price!

Thanks,
Adam

在 2019年5月9日,上午12:06,maximilien971 <decastejac@...> 写道:

Hello Adam
Very interesting!

Sorry if you still talk about it,  is there the case I have seen in the pics section?

73
Patrick
F6GWE

Re: D4D: Ready to Take Order

John M
 

Do you have a link to your paypal?

Re: DSB transceiver for Digital mode

Ron Stone
 

Adam,

Thanks for your helpful, informative responses.

So it sounds like the 40 meter version may be significantly more stable than the 20 meter version because of the lower frequency crystal.  In addition, the 40 meter crystal doesn't have to be pulled like the the 14.070 MHz crystal which eliminates another possible source of instability, correct?  Does this mean the heating resistor is more optional for 40 meters?

Also, what is your source for the 7.074 MHz crystals?

Thanks again for your help and I'm glad to see we can order now!

73,

Ron (KA3J)