AmateurRadio.com

YouKits Canada has announced the latest version of the TJ2B SSB handheld radio, that now also will provide cw mode after many requests from users of this radio.
The unit has also received some great reviews by the techs at ARRL test lab and have been published recently in QST.
Yimin strives to do his ultimate best with QC and trouble shooting as well as refunds and repairs. Not unusual for him to send a replacement radio before he has accepted the problem unit.
The HB line of radios has proven themselves over again in the field. many new projects are being developed by YouKits and we look forward to seeing these new items in the future.

http://www.youkits.com/#TJ2B_MK2_5_Band_SSB_Handheld_Transceiver

73 Fred Lesnick

VE3FAL

Since my original Fredbox 2m AM design, a number of derivatives have been designed and built around the world. This is what our hobby is all about. Although the original Fredbox worked well and its results surprised me, it was always ripe for further developments, which is healthy. My Sixbox was a 6m version and at some point, when fitter, I’d like to make a simple 10m AM version for local natters.

See https://sites.google.com/site/g3xbmqrp3/vuhf/fredbox for the original Fredbox. Click on the schematic to enlarge. Other derivative ideas are on my website www.g3xbm.co.uk.   By the way, it got its name from Fred G8BWI who was a disabled local in the Cambridge area back in the 1970s. Fred was a regular contact and he could talk for hours and hours and hours and hours zzzzzzzzzzz. RIP Fred.

G6ALB has reported some progress in his tests using 433MHz AM modules, although it looks like an external linear audio transistor stage may be necessary to get best AM (voice) sensitivity from the super-regen detector. On TX he is getting 10dBm from the TX module at 5V (more with higher supply voltages) although the mod seems to be a mix of AM and FM. Our first “DX” test will probably be from G6ALB to me using the voice modulated TX module. I’ll receive Andrew on my FT817ND initially. When the super-regen RX is sensitive with speech I’ll try to receive him with that. Super-regens should be sensitive on AM, but are usually poor NBFM detectors.  We are about 3km apart and both have V2000 verticals externally mounted. At 70cms these have gain.

Andrew has ordered 5  pairs of 433MHz AM modules (TX as well as RX) for not much more than £2 total from China. This makes each TX/RX pair very inexpensive. It amazes me that they can make these so inexpensively. I hope G6ALB succeeds in this venture. It would be good to be able to communicate with him using a really low cost 70cm transceiver. I expect Andrew will write up his results in an article for a UK magazine later.

It seems entirely possible that a complete 70cm AM transceiver can be made for just a few pounds based on these low cost 433MHz AM modules.

In many ways, 6m (50MHz) is an ideal band for experiments. Short RF leads are always good, but 6m is a forgiving band and you can get away with HF constructional techniques. It is 2MHz wide here in the UK and this means all speech modes can be fitted and used. The page below shows a number of links to 50MHz projects.

See http://www.pg1n.nl/articles.php?lng=en&pg=145 .

See also my Sixbox 6m AM transceiver .

This little top band AM transmitter and a companion receiver were first published in the GQRP club SPRAT magazine. This TX version was built by M0DAD. Where the noise floor allows, 160m AM is quite popular for local nets.  There is something nice about “rolling your own” builds and getting satisfying results without spending a fortune. For daytime local use 160m AM is a great mode and rigs are simple. I am still surprised that more is not made of AM on 10m at night for local nets here in the UK.

See http://www.delboyonline.co.uk/m0dad/construcion/poppet_top_band_am_transmitter.htm.

Well designed DSB transceivers are much simpler than SSB rigs as no SSB filters and mixing to final frequency is needed. They must not be over-driven to avoid a spreading signal. The PA needs to be linear too. These issues being carefully considered, you end up with a rig that has the same bandwidth as an AM rig but with a suppressed carrier. DSB transmitters are usually received as an SSB signal. The downside is that if a simple direct-conversion receiver is used then there is no rejection of stations sitting on the other sideband. So, they are best on quieter bands, rather than busy HF bands. Bands like 10m, 6m and 4m are probably good candidates.

Although not impossible, it is quite difficult to demodulate a DSB signal on a simple direct-conversion receiver. DSB rigs are ideal as simple transceivers to communicate with SSB rigs.

See http://home.alphalink.com.au/~parkerp/projects/projmicro40.htm

Also: https://aa7ee.wordpress.com/2013/10/19/the-vk3ye-micro-40-dsb-transceiver/

As you may recall, I am quite a fan of super-regen receivers. Nothing as simple is able to match their AM sensitivity, but they tend to have poor selectivity.

With the availability of very low cost 433MHz modules (TX and super-regen RX) designed for AM data, these modules could be ripe for conversion to ultra-simple 70cm AM voice transceivers. One local friend, Andrew G6ALB, is currently carrying out experiments to see if this is feasible. I hope to work him on 70cm AM using such a rig in the months ahead. Sadly, I am still too clumsy to do any building work – very frustrating.

I am wondering if anyone else has tried these modules in such a circuit? With a simple MMIC PA (50 ohms in and out) the power output could be lifted to around 25mW carrier or more. With V2000 verticals this should be good for local ranges. Even at the low milliwatt level from these QRPp modules several km range should be possible with co-linear antennas.

UPDATE 2310z:   I wonder what sort of power the TX modules typically produce with linear (speech) modulation rather than 5V square wave data modulation? Presumably much less than their rated power, so an add-on PA may be essential?