For the past few years I have been tinkering with many forms of indoor amateur radio antennas. I want to pass along these operating tips to try helping other operators in my position.
These are mainly observations on what has worked and what hasn't. Just because you can't have a full-blown station doesn't mean you can't be active on the HF bands.
Your choice of modes means a lot!
One of the biggest factors that affects your success using an indoor antenna on the HF bands is your choice of mode. While these tips are only suggestions, they have proven to be successful for me and have enhanced my stations performance.
CW means more DX!
Let's face it, for any sort of weak signal work, CW is the most efficient mode available to us today! Big DX'peditions usually concentrate most of their effort in CW for that reason.
With all of the varied modes available for HF operation available, CW has always been my best mode for success. I have been a ham for almost 30 years now and have always preferred CW. New hams aren't required to learn it to get their licenses but there are some factors that make it the perfect mode to use when working with limited antennas. Remember, Morse Code is a 100% duty cycle mode so your signal will stand a better chance of being heard than if you were using phone.
This fact became apparent to me many years ago when I used to do satellite operation. Back when I had outdoor antennas I became interested in operating satellites. There were many available like the RS-10, RS-12, and RS-15 that could be worked with basic HF/VHF equipment. They were low orbiting birds so passes came and passed in as little as 4 minutes. I always found it quite difficult to find and tune in a station using phone so switching to CW usually netted me more contacts per pass. Ever since then I would say that about 95% of my HF activities have been with CW.
Now with indoor antennas I find that CW allows me to hear and work signals that are weaker due to the reduced performance. There have been many DX'peditions where they operate on all bands and all modes. I can usually hear them on CW but find it hard to pick their signal out when operating phone on the same band.
RFI and digital modes
In my situation I have problems with PSK31 and RFI. Many times my PC will lock-up, programs will start themselves, and strange things can happen during transmission.
Thanks to modern technology and computer integration into the hobby, the digital modes have really helped when limited with indoor antennas. PSK31 is one mode where the error correction capabilities have really helped out. Plus, most PSK31 operation is at greatly reduced power which means you can run slightly higher than recommended power so that you can be heard. I have run PSK31 at about 30 watts and made many contacts without getting any reports of bad IMD.
RTTY is another mode of choice and FSK is recommended over AFSK. AFSK RTTY really uses SSB to transmit tones and I have found that any "Phone" mode generates more RFI both at the operating position and possibly with neighbors.
If you plan on operating using digital modes, how you cable your equipment is can make a big difference.
Always try routing RF cables away from computer cables. At my operating position, all RF cables come in above desktop height and go up. My PC and all of it's cabling is below desktop height.
Adding toroids around your keyboard and mouse cables to stop RFI at the PC.
Try using a different keyboard if you find RFI getting in. I had a no name type keyboard that went nuts when ever I transmitted. I switched that to a better keyboard (name brand) and eliminated the problem.
I don't use phone much
I would say that the total number of phone contacts is only about 10%. I generally use it on 75 meters to check into a local net. The ROC City net is a local net, Wednesdays at 8:00 pm on 3.825MHz.
Many people give up when trying to use an indoor antenna because they use phone. Remember, phone isn't a full duty cycle mode. Your power is directly related to the amplitude of your voice and ALC settings of the radio.
Another issue with phone is that there is a greater chance of creating RFI that could affect both your equipment and your neighbors televisions, stereos, phones, and computer speakers.
Not being a big fan of phone operation I can only suggest that you do what ever works for you. Don't give up just because one thing doesn't work. Band conditions are constantly changing so choose the band that has the best propagation for that moment.
Pick stations that have strong signals. If I hear a station that's at least 3db above the noise floor I can usually log a good contact. If it's a DX'pedition, I generally wait till the end after some of the "feeding frenzy" has cleared out.